AGRICULTURAL USE OF ALTERNATIVE WATER SOURCES ON THE ISLANDS OF TENERIFE AND GRAN CANARIA
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Horizon 2020 Societal challenge 5:
Climate action, environment, resource
efficiency and raw materials
Background report
AGRICULTURAL USE OF ALTERNATIVE WATER SOURCES
ON THE ISLANDS OF TENERIFE AND GRAN CANARIA
NEXUS WATER-ENERGY-FOOD
INNOVATION: ALTERNATIVE WATER SOURCES
(WP6.6)
Contributors:
Water Department (ITC)
www.magic-nexus.eu
AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
Please cite as:
Water Department – AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF
TENERIFE AND GRAN CANARIA – NEXUS WATER-ENERGY-FOOD
MAGIC (H2020–GA 689669). For being included into the Project Deliverable 6.7 (July 2018)
Disclaimer:
This project has received funding from the European Union’s Horizon 2020 Research and
Innovation Programme under grant agreement No. 689669. The present work reflects only the
authors' view and the funding Agency cannot be held responsible for any use that may be
made of the information it contains.
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AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
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Contents
Abbreviations ............................................................................................................................... 4
Summary ....................................................................................................................................... 6
1. Water in the Canaries ........................................................................................................... 7
1.1 Water culture .............................................................................................................. 7
1.2 Water policy in the Canaries........................................................................................ 8
1.3 Water planning, ......................................................................................................... 11
1.4 Water resources and requirements........................................................................... 12
2. Desalinated water in the Canary Islands ............................................................................. 19
2.1 Desalinated water on Gran Canaria .................................................................................. 20
2.2 Desalinated water on Tenerife.......................................................................................... 22
3. Reclaimed water in the Canaries ........................................................................................ 24
4. Energy consumption and costs of water resources ............................................................ 29
4.1 Energy consumption of desalinated water ................................................................ 29
4.2 Energy consumption of treated wastewater ............................................................. 30
4.3 Costs of the water ............................................................................................................. 31
5. Agriculture in the Canaries ................................................................................................. 32
5.1 Agricultural policy ...................................................................................................... 32
5.2 Agricultural production.............................................................................................. 37
6. Proposals for a study area .................................................................................................. 44
6.1 Justification of the choice of area .............................................................................. 45
6.2 Study area on Tenerife .............................................................................................. 45
6.3 Gran Canaria Case Study............................................................................................ 49
7. Proposals of pre-narratives and stakeholders .................................................................... 51
8. Selection of narratives ........................................................................................................ 56
10. Annexes .......................................................................................................................... 58
9.1 Summary of the Acequia Tenerife Conference ................................................................. 58
9.2 Summary of the Acequia Gran Canaria Conference ......................................................... 59
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Abbreviations
EDAR (Wastewater Treatment Station)
EDAM (Seawater Desalination Station)
IWRM (Integrated Water Resources Management)
CAP (Common Agricultural Policy)
POSEI (Community Support Programme for Agricultural Production in the Canaries)
PHI (Island Water Plan)
REA (Specific Self-Sufficiency Regime)
UE (European Union)
List of tables
Table 1 Water resources of the Canaries .................................................................................... 13
Table 2 Water demand in the Canaries ....................................................................................... 14
Table 3 Inventory of works to obtain water on Tenerife (2015) .................................................. 16
Table 4 Capacity, utilisation factor, production and specific consumption of the desalination
plants .......................................................................................................................................... 23
Table 5 Costs of management of water according to the treatment or extraction system in the
Canaries. ..................................................................................................................................... 31
Table 6 Aid to producers of tomatoes for export ........................................................................ 35
Table 7 Distribution of aid under POSEI by Banana Producing Organisation 2012 ...................... 36
Table 8 Top 5 of imports of food according to value, Canaries, 2009 (thousands of euros) ........ 41
Table 9 Amounts of water according to crops ............................................................................. 43
Table 10 Districts of the Canaries with alternative water resources .......................................... 44
List of figures
Figure 1 Garoé Tree ...................................................................................................................... 7
Figure 2 Relationship diagram of the water market system .......................................................... 9
Figure 3 Management of water resources in the Canaries .......................................................... 12
Figure 4 Evolution of water resources in the Canaries (1978-2012) ............................................ 13
Figure 5 Percentage of sectorial water demand by island ........................................................... 15
Figure 6 Graph of particular desalination plants in the Canary Islands ........................................ 19
Figure 7 Evolution of desalination capacity installed on Gran Canaria (m3/día) .......................... 20
Figure 8 Uses of desalinated water on Gran Canaria (2014) ....................................................... 21
Figure 9 Main desalination plants on Gran Canaria .................................................................... 21
Figure 10 Desalinated water vs reserves ..................................................................................... 22
Figure 11 Infrastructure of desalination of brackish and seawater ............................................. 22
Figure 12 Number of publicly-owned waste-water treatment plants in the Canaries (2009)...... 24
Figure 13 Diversity of tertiary treatments /regeneration for reuse in the Canaries (2009) ......... 25
Figure 14 Network of reclaiemd water on Gran Canaria ............................................................. 26
Figure 15 Reclaimed water network on Tenerife ........................................................................ 27
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AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
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Figure 16 Territorial ambits of reclaimed water supply ............................................................... 28
Figure 18 Distribution of installed electrical power at different stages of treatment .................. 30
Figure 19 Distribution of daily energy consumption (kWh/day) at a wastewater treatment plant
according to the stage of treatment............................................................................................ 31
Figure 19 Financing of the POSEI (Millions of. euros) .................................................................. 34
Figure 20 Ratio of aid with regard to the agricultural gross value added .................................... 38
Figure 21 Export of Canarian tomatoes tn .................................................................................. 39
Figure 22 Production of bananas in the Canaries ....................................................................... 40
Figure 23 Evolution of livestock in the Canarias (Number of head) ............................................. 40
Figure 25 Map of crops on Tenerife. District of Valle San Lorenzo – Las Galletas........................ 46
Figure 26 Map of crops on Tenerife. District of Valle Guerra - Tejina .......................................... 48
Figure 27 Map of crops in south east Gran Canaria..................................................................... 50
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Summary
In the Canaries, historical agricultural activity for export has been conditioned by the
availability of water resources, which have been since the very beginning linked to the water
market managed by the private sector which financed the construction of water channels,
dams, water-mines and wells. Since the 1960s, the demand for drinking water has been
increasing constantly as a consequence of tourism-related activities and the rise of population.
New ways of acquiring water, referred to as alternative water sources, have been developed,
which have contributed to reducing the pressure on aquifers and regulating the price of water
on the market. Alternative water sources in this context are desalination and reclaimed water.
Desalinated seawater, with which we supply urban and tourist areas, has had a historic
implantation in the Canary Islands. It has recently begun to be used for agricultural purposes.
Secondly, reusing water after wastewater treatment, is considered as a sustainable way of
obtaining water for agriculture and gardening purposes. Currently, due to technological
improvements, alternative water resources are put forward as a feasible solution to supply the
water needs for export crops, and at the same time to favour an increase in the area of other
crops devoted to the internal market. In this way, the degree of self-sufficiency in food (food
sovereignty) is improving.
This document aims to provide a general overview of the use of alternative resources in
agriculture in the Canaries, with a bibliographic review including general and sectorial data
related to: water demand, desalinated and reclaimed water, the policies of water and
agriculture in the Canaries, and characterising cases in Tenerife and Gran Canaria. For these
purposes, areas or districts which have alternative water resources for agricultural use have
been located, to dig deeper into the narrative analysis regarding these alternative water
sources and agriculture.
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1. Water in the Canaries
Water has always been key to understanding wealth in the Canaries. It is not by chance that
the islands which had a greater number of springs had greater economic and population
development than the others1. This has been changing since the late 20th century, and
technological development has made it possible to obtain water from the sea and the re-use of
wastewater, thus separating agricultural development from exploitation of natural water
resources.
The management of water in the Canaries differs according to the island, as a matter of its
orography, the (micro)climates, the water demands (depending on population growth) and the
economic development of each island’s territory.
1.1 Water culture
The management and uses of water in the Canaries have created a culture of their own, rooted
in the aboriginal society of the islands which continues to be present today. The difficulty in
obtaining the resource gave rise to a range of systems for its capture, storage and distribution;
adapted to the climatic, hydro-geological peculiarities and the agricultural demands of each
island, which are mainly included as part of the water heritage of the Canaries.
The first symbol of water culture in the islands is the Garoé tree, on El Hierro island. A sacred
tree for the Canarian native, pre-Hispanic inhabitants with which they supplied themselves
with water which was collected by the branches of the tree, capturing water from the mists
(the sea of clouds), which are caused by the Trade Winds.
Figure 1 Garoé Tree
Source: Prints of the Garoé tree, Benzoni 1572 and de Bry 1596.
It is not possible to understand the culture of water in the Canary Islands without taking into
account agriculture, due to the fact that water resources were linked to agricultural exports
1
Rodríguez, W. (1996) Agua y agricultura en Canarias. Ed: Centro de la Cultura Popular de Canarias
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from the very moment colonisation happened in the islands, in the late 15th century. The
lands with the most abundant resources were taken under the control of the governing élite,
made up of the conquerors from Castile and those who had financed the conquest, among
others, the Genoese such as Mateo Viña on Tenerife, who introduced sugar cane to the
Canaries, or families of Flemish origin such as the Van de Walles, Massieu Vandales and
Monteverdes on the island of La Palma, who produced sugar cane2. The economic
development based on exports of sugar increased water requirements not only for the
irrigation of the sugar-cane plantations but also for the operation of the sugar refineries.
The Heredades or Heredamientos de Aguas arose as unifying organisations of owners of the
rights of water from streams and springs, which, via a complex network of irrigation channels
or tarjeas, distributed the water to reservoirs and tanks.
Finally, the development of the new export crops at the beginning of the 20th century, such as
the banana and the tomato, which diversified the export business increasing the number of
small producers; increased the pressure once again on underground water resources. At that
moment, it became necessary to invest in water infrastructure, by increasing the number of
galleries and wells3, which had, until then, been devoted to domestic consumption in areas
where there were no nearby springs or sources of water. In the case of Gran Canaria, it was
mainly the wells which were dug all over the island which covered the needs of the new
crops4, increasing the energy requirements and the over-exploitation of the aquifers up to the
present.
This process of increasing over-exploitation of natural resources on islands such as Gran
Canaria and Tenerife led to a situation of speculative increases in the price of water for
irrigation and a scarcity of water supply after the mid-20th century. This situation led to
introduce first desalination and later reclaimed water, to satisfy the demand .
1.2 Water policy in the Canaries
The application of water policies in the Canaries differs in each island. However, the policies
have the function of regulating the water market in the Canary Islands, which is a mixed
market with both public and private participation, and in which there have been constant
conflicts regarding rights of obtaining, managing and marketing a resource which is of a public
nature, as is water.
Water markets in the Canary Islands
In the water market of the Canaries, many agents are involved, who share out water rights;
both the private rights, as in the case of the heredamientos, irrigation communities,
companies; and individuals with their the public rights, the public water management
2
Perez, J. (2013). El azúcar y su introducción en las islas atlánticas. Volumen II Ed: Cabildo Insular de La
Palma. Recuperado de: https://dialnet.unirioja.es/descarga/libro/560916/2.pdf
3
A gallery is a horizontal shaft into the aquifer with the aim of obtaining water. While wells are drilled
vertically. They both exploit renewable water resources which would otherwise not have been taken
advantage of.
4
Rebollo, M. (2013). El tomate en Gran Canaria. Cultivo, empresa, aparcería y exportación. Ed: Anroart
Ediciones. Madrid.
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companies (BALTEN) and the Water Councils of the islands, which are the equivalent to the
River Basin organisations of the Spanish State.
For there to be a market of water use rights, there must be a system of assignment of licences,
permits, titles or rights, which is developed by the market5. In this regard, one of the
characteristics of the traditional regime of water use in the Canaries is the system of
concessions by means of which over 85% of the total water resources is of a private nature.
The capture, assignment, distribution and use of underground water has been totally
undertaken by private initiative, using the traditional Canarian legal framework, the Canarian
Water Act.
Another of the conditioning factors of a water market is the existence of an administrative
system which registers the ownership and the transfers of ownership of those rights and which
controls and quantifies their use11. In this regard, the function of the Public Administration is
that of mediating in the conflicts between private parties and ensuring that the current law is
respected. It also has the function of intervening in the water market so as to prevent
situations of oligopoly, reducing the price and improving the distribution. With this purpose,
on Tenerife, the publicly owned company BALTEN was created, which has become an
instrument to manage the pools and water networks on the island. This publicly owned
company is a supplier and a distributor at the same time, thus regulating the price of water on
the island.
The following diagram shows the relationship between the different actors which participate
in the Canarian water market:
Figure 2 Relationship diagram of the water market system
Source: Island Water Plan of Tenerife. Second Cycle (2015-2021).
5
Simpson y Ringskog (1997) Water Markets in the Americas
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Integral Management of Water Resources
The IWRM (integrated water resources management) is a holistic approach to the
management of water resources in a sustainable manner, guaranteeing economic
development and social wellbeing. In the Canaries, implementing the approach of the IWRM is
of vital importance, due to the large number of agents who act in the water sector, to the
vulnerability of the territory and the scarcity of water, which put a brake on the economic
development of the islands.
There are different economic visions6 of the water resources which classify them as:
Ø A production factor, which is within an institutional framework which reflects interests
and values to which a cost is applied.
Ø A financial resource, given that it is a limited natural resource from which profitability
is obtained similar to that of financial assets.
Ø An eco-social asset; understanding this to be the capacity which water has to satisfy a
set of economic, social and environmental functions.
Without a doubt, in the Canaries, water can be considered a production factor which is both
public and private; a financial resource due to the speculative nature of private management;
and an eco-social asset due to the importance of the resource for socio-economic
development and the preservation of the environment. In this last line, the Framework
Directive of Water (Directive 2000/60/CE) sets down that water is not a commercial property
as others are, but a property which must be protected, defended and treated as such.
A characteristic of the island environments is their high degree of vulnerability and for this
reason water policies must be based on sustainable approaches, on prevention of
contamination and improvement of ecosystems and available resources, establishing the
ownership of water as public, as water is a public merchandise. However, management may be
private, public or collective, given that there is no scientific reason which shows the greater
efficiency of any particular form of management over the others, and there are many
examples in the Canaries of different systems of management of the resource.
The reclaimation and desalination of water are two of the strategies capable of supplying
additional resources and substantially improving the management of the quantity and quality
of the available resources. Agricultural irrigation constitutes the main application of reclaimed
waters in the Canaries and the management is carried out by public organisations such as the
Island Water Council on Gran Canaria or BALTEN on Tenerife. The Canary Irrigation Plan
contemplates numerous actions for the use of new resources for irrigation, mainly what is
located in coastal areas, due to the great water requirements of crops and the lack of
underground water resources.
In short, it is to be recommended that this management should be carried out by a centralised
organisation which allows more exhaustive control and monitoring of facilities, the physical
and chemical and bacteriological quality of the water, the control of flows and pressures of
supply to users and advice to them.
6
Aguilera Klink, F. (2008). La nueva economía del agua. Madrid: Catarata
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Price of water
When looking at the origin of water, it is evident that the cubic metre has different costs and
the price arises not just from the way that the resource is obtained , but scarcity or abundance
also has an influence, and even more so because each island is a non-homogeneous water
system due to the fact that the movement of water is conditional on the availability of the
supply networks. In the same way, the average costs estimated of water vary according to the
island, increasing as you approach the easternmost islands.
For purposes of orientation, on Tenerife the price of a cubic metre of water for irrigation is
around 0.50 - 0.70 €/m3, while on Gran Canaria, a cubic metre of underground water varies
between 0.36 - 0.58 €/m3 7. On the other hand, despite the fact that production costs for
desalinated and reclaimed water depend on many factors, such as the scale, and the operating
costs of the manager of the facility among others. The price of reclaimed water made available
to farmers for irrigation is also influenced by a subsidy of the Island Corporation. The final
price of public water from alternative resources is around 0.35 - 0.55 €/m3 for reclaimed water
and 0.60 - 0.75 €/m3 for desalinated seawater.
1.3 Water planning,
In the Canaries, there is a special regime of Water Law which is set out in the "Estatuto de
Autonomía" (Law granting autonomous powers of government) and the Complementary
Transfers to the Canaries Act, which gives the Canary Islands autonomy regarding water. This is
the existing legal arrangement in the Canary Islands:
• Act 12/1990, of 26th July, on Water.
• Act 10/2010, of 27th December, in modification of Act 12/1990, of 26th July, on Water.
• Act 44/2010, of 30th December, on Canarian waters (review).
In this regulatory framework, it is set down that water is subordinate to the general interest
for its use in the proper quantity and quality, respecting the environment of the islands. It is
considered to be a unitary resource, constituting one water area per island, administered by
the Island Water Councils attached to the Cabildos (Island Corporations), .and where planning
is materialised in the Island Water Plans. These are some of the functions of the Island Water
Council: 8:
ü Preparation of budgets, legislation and plans.
ü Control, custody and management of water in the public domain.
ü Services of advice, execution and control of water programmes and works.
ü Setting of prices for water and transport of water.
ü The exploitation of making use of water.
ü In general, all work relative to the administration of water on the island that is not
reserved to other bodies.
7
AQUAMAC Project. Guide to Water in European Macaronesia (2008).
8
Department of Agriculture, Livestock, Fishing and Water of the Canary Islands Government.
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According to the Water Framework Directive in Europe, the supply of water is a service of
general interest. Apart from water policies, they must be based on sustainable approaches,
for prevention of contamination and improvement of ecosystems and available resources.
The bodies that participate in the management of water may be either public or private. In
Figure 5, the management of water resources in the Canaries is shown, from supply to
drainage, including the responsible bodies involved in each process.
Figure 3 Management of water resources in the Canaries
Source: Island Water Plan of El Hierro. Second Cycle (2015-2021); General Water Directorate.
A historical demand in the islands is to make the water plans and the island councils living
organisations with participation in all social sectors, in which investments in water with a
general interest for the population are prioritised.
1.4 Water resources and requirements
Water resources on volcanic islands can be divided into four categories, those which come
from underground water masses, those that are from surface run-off, those obtained from
desalination and those reused after treatment.
According to the latest information from 2015 on the PHI of the Second Cycle in the Canaries,
it amounts to 494.50 hm3/year, with great variability in obtaining the resource between islands
as is shown in Table 1.
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Table 1 Water resources of the Canaries
WATER RESOURCES OF THE CANARIES (hm³/year)
TOTAL
Groundwater Surface Desalination Reuse
ISLAND
Lanzarote 0.36 1% - 0% 24.40 93% 1.37 5% 26.13 5%
Fuerteventura 0.27 1% - 0% 26.50 88% 3.30 11% 30.07 6%
Gran Canaria 65.50 41% 10.70 7% 72.00 45% 12.30 8% 160.50 32%
Tenerife 159.60 81% 0.90 0% 26.60 13% 11.10 6% 198.20 40%
La Gomera 5.93 63% 3.41 37% - 0% - 0% 9.34 2%
La Palma 62.30 94% 4.20 6% - 0% - 0% 66.50 13%
El Hierro 2.20 58% - 0% 1.54 41% 0.02 1% 3.76 1%
TOTAL
CANARIAS
296.16 60% 19.21 4% 151.04 31% 28.09 6% 494.50 100%
Source: Island Water Plans. Second Cycle (2015-2021)
The largest resource in the islands is groundwater (60% of the total). In the past, the increase
in demand was offset by drilling new galleries and wells. However, currently the exploitation of
underground resources has decreased in favour of other strategies such as desalination and
reuse, as is made clear in the data in Figure 4.
Figure 4 Evolution of water resources in the Canaries (1978-2012)
Source: Canary Islands Government. Department of Agriculture, Livestock, Fishing and Water.
The water requirement in the Canaries can be grouped in five categories, according to the
information available in the Island Water Plans of the Second Cycle9, and they are as follows:
• Urban; corresponding to urban supply of cities, towns and villages.
• Tourism; this is the demand for water in holiday accommodation (hotels, apartments,
etc.)
9
We have attempted to make the categories as homogeneous as possible given the diversity of island
water systems.
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• Recreational; this is the use of water in recreational and leisure facilities (theme parks,
golf courses, etc.)
• Industrial; water for industrial uses
• Agricultural; water demand from the agricultural and livestock sectors.
• Other uses; demand other than that in the foregoing categories.
According to the estimates of the Island Water Plans of the Second Cycle in the Canaries, in the
year 2015 around 470 hm3 were required. This amount can be broken down to different
figures for each island that are very different in terms of socio-economic development, which
is also reflected in the differences between the water demand on each island, as is shown in
Table 2.
Table 2 Water demand in the Canaries
WATER DEMAND IN THE CANARIES (hm³/year)
Agricult Other TOTAL
Urban Tourism Recreation Industrial
ural uses ISLAND
Lanzarote 10.19 49% 8.47 41% - 0% 0.67 3% 1.51 7% - 0% 20.84 4%
Fuerteventura 15.51 73% - 0% - 0% 0.36 2% 1.13 5% 4.23 20% 21.23 5%
Gran Canaria 62.10 39% 16.40 10% 12.90 8% 8.30 5% 60.80 38% - 0% 160.50 34%
Tenerife 71.60 36% 19.60 10% 3.70 2% 6.70 3% 85.60 43% 11.20 6% 198.40 42%
La Gomera 2.31 31% - 0% - 0% - 0% 5.03 69% - 0% 7.34 2%
La Palma 6.49 11% 2.01 3% - 0% - 0% 49.73 85% - 0% 58.23 12%
El Hierro 1.47 42% - 0% - 0% 0.13 4% 1.91 54% - 0% 3.51 1%
TOTAL
CANARIES
169.67 36% 46.48 10% 16.60 4% 16.16 3% 205.71 44% 15.43 3% 470.05 100%
Source: Island Water Plans. Second Cycle (2015-2021)
Of the total amount of water required in the year 2015, 44% was devoted to the agricultural
sector and 46% to the domestic and tourism sector, and to a lesser degree the recreational
sector with 45 and the industrial with 3%.
This percentage distribution is different in each of the islands, except Tenerife and Gran
Canaria (see Figure 5), where apart from having similar demand percentage, they are the
islands with very similar socio-demographic and economic indicators.
14AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
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Figure 5 Percentage of sectorial water demand by island
Source: From the Island Water Plans. Second cycle (2015-2021). Own elaboration.
From these data, we can conclude that there is a close link between water resources and
economic development. In short, the management of resources is a suitable reflection of the
model of development of a territory and the society living there.
Scarcity of water in the Canaries
The scarcity of water is one of the phenomena which is becoming generalised all over the
planet, with many causes. In the islands, one of the main causes is the exhaustion of the
aquifers and/or their contamination10. The conditions of scarcity have been solved since the
mid-20th century with the construction of large water infrastructures devoted to storage
(reservoirs), distribution (canals and pipes), and the extraction of water directly from the
aquifer (wells and galleries).
However, the growing demand for water due to the increase in population and tourism-related
and agricultural activity, has reduced the natural resources as a consequence of over-
exploitation. This problem is clearly reflected on Tenerife, where over a thousand galleries and
1,500 wells (see Table 3) have been drilled, almost half of which are now dry. This is due to the
lowering of the phreatic level of the masses of water in the aquifer in the case of the galleries,
and saline intrusion into the coastal aquifer in the case of wells.
10
Rodríguez, W. (1996) Agua y agricultura en Canarias. Pub: Centre for Popular Culture in the Canaries
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Table 3 Inventory of works to obtain water on Tenerife (2015)
Source: Island Water Plan on Tenerife (2015-2021). Second Cycle.
On Gran Canaria, there is a similar problem with intrusion due to over-exploitation of the
coastal aquifer. Many of the wells have ceased to be used, or alternatively some are still
working with desalination systems for brackish water, which in general terms only makes the
problem worse. For this reason, the trend is to reduce or cease their use so as to attempt to
reverse the processes of generalised descent of the phreatic level in the interior and of saline
intrusion in the coastal aquifer. On the other hand, these masses of underground water are
affected by the presence of nitrates, deriving from the percolation of agricultural irrigation
waters (with nitrogenised fertilisers) and liquid wastes (manure) from livestock activities.
There are a number of rules and regulations in Europe11 and also Spanish rules and regulations
to prevent this kind of contamination of masses of underground waters, which on the other
hand are of difficult application in limited territories such as oceanic islands, where agricultural
and livestock activities compete for the use of the land with urban and tourism-related
settlements, which tends to concentrate them. Furthermore, volcanic islands have different
kinds of soil and techniques for harnessing water which differ from those on continental
territory.
11
Directive 2000/60/CE from the European Parliament and the Council, of 23rd October 2000, setting
down a community framework of action in the sphere of water policy.
Directive 91/676/CEE of the Council, of 12th December 1991, relating to the protection of water from
contamination caused by nitrates used in agriculture.
16AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
Surface run-off
The islands do not have any rivers or streams with sufficient flow (excepting the river from the
Caldera de Taburiente), with the result that the storage of surface run-off is a minority option.
Additionally, the volumes are lower to those obtained from groundwater water. However, on
Gran Canaria and La Gomera, this kind of resource is used for agricultural supply, in an area
where the steep contours of the island and the impermeable substrates make up for the oldest
areas used for the construction of reservoirs (or dams. These areas also drag barriers for the
regulation of the flow and storage of water, due to high levels of surface water demand.
The greatest capacity for storage of surface waters is on the island of Gran Canaria, with
almost 43 hm³, with the largest being the Soria reservoir with a capacity of almost 32 hm³. It is
curious to note that this reservoir is one of the fifteen highest arch dams in Spain12.
Figure 1 Soria reservoir (Gran Canaria)
Source: AIDER
12
Santamarta, J.C. et. al. (2013) Hidrología y recursos hídricos en islas y terrenos volcánicos. Métodos,
técnicas y experiencias en las Islas Canarias. Ed: College of Mountain Engineers. Madrid. Recovered
from: http://oa.upm.es/19965/1/Libro_digital_AGUAS.pdf
17AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
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Losses of water
Another important subject the loss of water from the network, which rises situations of
unsustainability in some areas of the islands. It seems contradictory to speak of scarcity of
water and difficulty of obtaining water resource, when losses in the urban and agricultural
networks are so high, that if they were reduced, it would not be necessary to install new
desalination plants. On Gran Canaria, losses in urban supply vary between 17% in San
Bartolomé de Tirajana and 42% in Arucas and are concentrated in areas which have more
resources available.
Source: Island Water Council of Gran Canaria
On Tenerife, the water not taken in by the supply service (among which are the real losses)
amounts to around 29.3% on average, of which 7.8% correspond to the service, and 21.5% to
the distribution service13.
13
Island Water Plan of Tenerife. Second cycle (2015-2021)
18AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
2. Desalinated water in the Canary Islands
The efforts made in obtaining groundwater water have not been sufficient to cover the
demand on some islands, and since 1964, with the introduction of the first desalination plant
on the island of Lanzarote, the cycle of use of non-conventional or alternative water resources
began (desalination and reclaimed water). It has made it possible to supply a part of the
agricultural demand and guarantee the supply to the growing urban and tourism-related
sectors.
In Figure 2, the landmarks for desalination in the Canary Islands are shown, including the first
thermal desalination plants and the new plants for desalination with membranes by means of
reverse osmosis.
Figure 6 Graph of particular desalination plants in the Canary Islands
Source: Carmelo Santana Industrial Engineer
19AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
This technological development in the water sector has been accompanied by a change in the
policies and management of water in the Canaries. One example is the institutional declaration
in the Canaries so that desalination is an activity of General Interest to the State and which
involved, in 1984, the start up of the Desalination Programme in the Canaries with financing by
the Ministry of Public Works and the Canary Islands Government. From that moment on, it was
possible to appreciate the decisive commitment of public investment towards desalination as
is shown in Figure 7, which makes clear the increase in desalination capacity on the island of
Gran Canaria.
The use of water from desalination plants has been increasing as the technology of the water-
treatment stations has evolved, improving the membrane technology, with greater capacity
and lower cost, and implementing processes that are more efficient in energy terms14.
In the agricultural sphere, the use of desalinated seawater, which two decades ago was
restricted to agriculture as a result of the high costs, has undergone a notable
technological evolution, improving its efficiency and giving rise to a reduction in price, with
the result that the resource has become highly competitive with regard to the price of
underground water on some islands. This is especially significant when the seawater
desalination plants are associated with sources of renewable energy, which reduces the
energy cost.
2.1 Desalinated water on Gran Canaria
Gran Canaria is the Canary Island which has the largest capacity of desalination plants
installed. According to data from 2012, the island has over 350.000 m3/day of desalination
capacity. This has meant a qualitatively important leap as is shown in Figure 7.
Figure 7 Evolution of desalination capacity installed on Gran Canaria (m3/día)
Source: Island Water Council of Gran Canaria
With this elevated capacity, there is an annual volume of desalinated water of 72 hm3/year, of
which 8.7 hm3/year are devoted to agricultural use as is shown in Figure 8.
14
Gómez-Gotor, A., Del Río-Gamero, B., Prieto Prado, I., Casañas, A. (2018). The history of desalination
in the Canary Islands. Desalination 428, 86–107
20AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
Figure 8 Uses of desalinated water on Gran Canaria (2014)
Desalada;
hm³/año Urbano; 45,2
Desalada;
Desalada; Turístico; 12
Agrario; 8,7 Desalada;
Desalada; Industrial ; 5
Recreativo; 1,1
Source: Island Water Council of Gran Canaria
For this purpose, a large amount of infrastructure has been put in place, distributed around
the main centres of population including particularly the Las Palmas III desalination plant, with
a capacity of 114,000 m3/day. In Figure 9, the main public and private desalination plants on
the island are shown, together with their capacity in m3/day and their location, some of which
are solely used for agriculture.
Figure 9 Main desalination plants on Gran Canaria
Source: Island Water Plan of Gran Canaria (2009-2015)
21AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
The introduction of desalinated water into the island water cycle has also made it possible to
maintain water reserves and reduce the effects of over-exploitation of the aquifer, as is shown
in Figure 10, which shows a simulation of the decreasing trend of the water reserves of the
aquifer if the desalination of seawater had not been developed (discontinuous red line).
Figure 10 Desalinated water vs reserves
2500 SPA15
2.125 hm³ Desaladas
2000
Reservas
Reservas en hm3
1500
1000 2011
886 hm³
500
0
-462 hm³
-500
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
1972 SPA15 2006
Años
Source: Island Water Council. of Gran Canaria
2.2 Desalinated water on Tenerife
On Tenerife, the water resources generated from desalinated water amounted to 26.6 hm³ in
2015, which amounts to 16% of the total resources. In the period 2000-2010, the volume of
desalinated water increased notably, with an annual growth of 16.4%. Apart from devoting
these resources to cover urban demand, there were different uses for irrigation, whether
agricultural or golf courses. It is significant that in the year 2010, the demand from golf courses
rose to 3 hm³, which represents nearly 2% of the island water demand.15.
Figure 11 Infrastructure of desalination of brackish and seawater
Source: Island Water Plan of Tenerife. Second Cycle (2015-2021)
15
Island Water Plan of Tenerife. Second Cycle (2015-2021)
22AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
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In Table 4, the Seawater desalination plants which give service on the island for the
desalination of water for urban use are shown.
Table 4 Capacity, utilisation factor, production and specific consumption of the desalination
plants
Source: Island Water Council of Tenerife
There are also four publicly-owned portable desalination plants and twenty-six privately-
owned authorised plants. the costs of desalinated water are located between 0.58 - 0.75 €/m3,
greater than the average price of underground water.16.
16
Memories of BALTEN 20 años (2008). Cabildo of Tenerife.
23AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
3. Reclaimed water in the Canaries
Reclaimed water for irrigation is the most recent and controversial resource, replacing the
extraction of groundwater, and it has an additional environmental value in the Canaries as it
significantly reduces dumping in the sea both waste waters and the brine produced by the
desalination plants (from the wells or the tertiary stage at the treatment plants)
Water treatment and the potentiality of obtaining reclaimed water is a strategic factor in the
Integral Management of Water Resources. In the Canary Islands, there are around 100
publicly-owned waste water treatment stations (EDAR) attached to the Island Water Councils
or Local Authorities. The set of facilities is very heterogeneous, both from the technological
point of view, the degree of treatment and dimensions, and from the point of view of
ownership and management. Among all the Wastewater Treatment Plants in the Canary
Islands, a level of reuse of 28.09 hm3 of wastewater was achieved, that is to say, 65 of all the
water resources in the Canaries in 2015.
In Figure 12, the approximate number of Wastewater Treatment Plants per island is shown.
Between 35 and 40% of the existing Wastewater Treatment plants have a capacity equal to or
greater than a population equivalent of 500017. This percentage varies notably according to the
island in question. Only on Gran Canaria, Tenerife and Lanzarote are there facilities with a
capacity greater than a population equivalent of 50,000.
Figure 12 Number of publicly-owned waste-water treatment plants in the Canaries (2009)
Source: General Directorate of Water Canary Islands Government.
In general terms, over 25% of the wastewater treatment plants in the Canary Islands have a
tertiary treatment which favours the reuse of water. The great majority of the systems are
among the group with a capacity equal to or greater than a population equivalent of 5000.
From the available information, without taking into consideration the disinfection systems, the
great diversity of types of tertiary treatment and combinations applied in the Canaries stands
out. In Figure 13, the different possible combinations are shown. The characterisation of the
tertiary treatments for reuse is of transcendental importance from the energy point of view as
17
This unit of measurement is based n the amount of contamination emitted per person and per day. An
equivalent population of one is 60g of DBO5 per day for 150L/day of volume of used water.
24AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
in some cases, they can double the energy demand of a waste water treatment plant. It is
worth emphasising that the majority of the treated water which has been reused comes
originally from desalinated water.
Figure 13 Diversity of tertiary treatments /reclamation for reuse in the Canaries (2009)
Source: TECOAGUA Project, ITC
The planned reuse of treated wastewater began in the late 1980s on Tenerife and Gran
Canaria with the aim of substituting for the underground resources and satisfying the demand
for water, especially irrigation in agriculture. For this purpose, the necessary infrastructure has
been created with which to treat the wastewater from the main centres of population on the
islands, distributing it via networks in the areas devoted to agriculture, parks and gardens and
the golf courses in tourist areas.
After so many years of experience it is clear that a good strategy in the management of water
is treatment and reuse, due to the fact that the same volume of urban water can be used for
certain agricultural and industrial uses. In this way, the urban consumption might be
subtracted from the calculations and estimates of water needs18, thus achieving a more
sustainable water balance.
18
Aguilera Klink, F. (2008). La nueva economía del agua. Madrid: Catarata.
25AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
In the Irrigation Plan in the Canary Islands (2014-2020) a series of actions are spelt out to
encourage reuse of treated water, some of which are19:
- Including facilities to affect the tertiary treatment necessary for the production of quality
water.
- Including facilities for water desalination, beyond what is set down in the regulations and in
accordance with the requirements of crops for watering.
- Establishing new networks exclusively for reclaimed water and making it possible for each
farmer to opt for the water which has traditionally been supplied, the new resource or if he so
wishes a mixture of the two.
Reclaimed water on Gran Canaria
On Gran Canaria, there is a network of 315 km which extends from the north to the south-east
of the island and has some 2,100 users in 90 communities of irrigators. The network connects
27 water treatment plants with a total capacity of 8 hm³/year, of which six have tertiary
treatment and a capacity for reclaimation of 35,000 m³/d. The network also has twenty-five
pumping stations and forty-one water tanks with a capacity of 455,000 m³.
On the island, a total of 12.3 hm3/year are reused directly, which means 8% of the water
resources. In the coastal area, 90% of the wastewater is treated, with 35% being converted
into reclaimed water20. About 80% of the treated wasteewater which is reused comes from
five large treatment plants in the boroughs of Las Palmas de Gran Canaria, Telde, Agüimes, San
Bartolomé de Tirajana and Mogán21. The main purpose is the irrigation of parks and gardens
and golf courses in the south of the island, while in the east and the north, it is reused in
agricultural irrigation.
Figure 14 Network of reclaiemd water on Gran Canaria
Source: Island Water Council of Gran Canaria
19
Irrigation Plan of the Canaries (2014-2020). General Directorate of Agriculture and Rural Deveopment.
Government of the Canary Islands. Obtained from:
http://www.gobiernodecanarias.org/agricultura/docs/desarrollo-rural/regadio/PRC_avance.pdf
20
Island Water Council of Gran Canaria (2017).
21
Updated study of the situation of use of treated waters in Macaronesia (2006).
26AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
Reclaimed water on Tenerife
The southern area of Tenerife was the pioneer, over twenty years ago, in the agricultural use
of treated wastewater. This was possible due to the construction of a treated wastewater
network joining the Santa Cruz wastewater treatment station (operating flow of 21,820 m³/d),
which is fed from the metropolitan area (boroughs of El Rosario, La Laguna and Santa Cruz de
Tenerife), with the waste water treatment plant of Adeje-Arona (operating flow of 10,950
m³/d) which is fed from the boroughs of Adeje and Arona in the south of the island. The
wastewater treatment plants are connected by a pipe 61 km in length joining the regulation
tank of El Tablero in Santa Cruz de Tenerife, with the San Isidro pool in the borough of
Granadilla de Abona, which supplies reclaimed water to an extensive area of cultivation of
tomatoes. The network ends at the pool in Valle de San Lorenzo in the borough of Arona,
which includes a desalination station (tertiary), and supplies almost 1,000 hectares of crops,
mainly bananas in Valle de San Lorenzo and Las Galletas22. The reclaimed water is distributed
in the following proportions: 66.4% to agricultural plots, 21.9% to golf courses, 11.2% to parks
and gardens and 0.5% for other uses ⁴. The volume of reclaimed water reused on the island
reached 11.1 hm³ in 201523.
Figure 15 Reclaimed water network on Tenerife
Source: BALTEN
Currently, the supply of reclaimed water is planned in other parts of the island, such as Valle
Guerra, the north-west or the Orotava Valley.
22
Memorias de BALTEN 20 años (2008). Cabildo de Tenerife.
23
Island Water Plan of Tenerife. Second Cycle (2015-2021).
27AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
Figure 16 Territorial ambits of reclaimed water supply
Source: Island Water Plan of Tenerife. Second Cycle (2015-2021)
28AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
4. Energy consumption and costs of water resources
The IWRM (integrated water resources management) of the Canary Islands requires more and
more energy resources for activities such as the capture of water from the aquifer using wells,
the desalination of seawater, transport and distribution to the points of consumption, as well
as for its treatment in the water treatment systems and its subsequent reclamation and
reintroduction into the system.
4.1 Energy consumption of desalinated water
The growing demand for alternative water resources involved an increase in energy demand
required to supply them, as there is a relevant nexus in the Canaries between energy and
water. The public desalination plants alone consume between 5 and 10 per cent of the
electrical energy in the grid in the Canaries. On Tenerife, this quantity is about 1.35%, while on
Gran Canaria, with a larger number of facilities, it amounts to 5.3% of electrical energy24.
In terms of the integral water cycle, this value of energy demand can reach 15-20% of the total
consumption of electrical energy, in which processes of desalination of seawater, transport
and distribution are included as far as the points of consumption, the collection of wastewater,
treatment and reclamation. For example, in a desalination plant, energy may represent from
50 to 60 per cent of the total cost of the operation, without considering the costs of
depreciation. In the same way, it is necessary to bear in mind the high losses in the water
distribution networks, which in many cases are close to or even greater than 50%, and which
also involve a considerable energy loss in the system.
The average specific consumption of energy for the desalination of water in 2011 was 4.89
kWh/m3 (desalination and first pumping of desalinated water). In the largest production centre
in the Canaries (Las Palmas III) the specific consumption is around 4.2 and 4.8 kWh/m3. There
is only one production centre capable of desalinating water at a cost of below 4.0 kWh/m3, the
Arucas – Moya desalination plant on Gran Canaria with 3.72 kWh/m3. Today there are still
several production centres which maintain in operation systems of energy recovery with a
turbine or which have low surface membranes, which makes it difficult to get below 4.0
kWh/m3 of average consumption in the desalination process.
In this regard, it must be borne in mind that the foreseeable scenarios of scarcity of fuel will
affect the water supply, which is dependent upon energy, while the changes in rainfall as a
consequence of climate change will reduce the availability of the resource. This means a large
risk in the integrated management of water resources in the Canaries, as this endangers the
environmental and economic sustainability of the supply systems, with the result that the
most viable option to reduce the vulnerability of the islands is to link the obtaining and the
availability of water to renewable energies.
24
Datos de Estadísticas Energéticas Canarias (2011).
29AGRICULTURAL USE OF ALTERNATIVE WATER ON THE ISLANDS OF TENERIFE AND GRAN CANARIA –
NEXUS WATER-ENERGY-FOOD – CASE STUDIES
4.2 Energy consumption of treated wastewater
There are no studies in the Canaries which can give a good idea of the total energy
consumption associated with water treatment and reclaimation of water, with the result that
it is not possible to estimate the water-energy link. Privately, the ITC carried out in 2011, as
part of the TECOAGUA (CENIT) project, under the leadership of Abengoa Water25, an energy
study of five wastewater treatment plants in the Canaries of different sizes, from which a
number of conclusions could be drawn.
The average relative energy demand at the treatment plants studied, without taking into
consideration tertiary treatment, is close to 0.7 kWh/m3 of capacity of the facility while in
those treatment plants which have tertiary treatment based on desalination to produce
reclaimed water, their consumption ratio is greater than 1.2 Wh/m3 of capacity of treatment.
Taking as an example one of the treatment plants studied, it is possible to appreciate, in Figure
15, the distribution of electrical power installed at each stage of treatment.
Figure 17 Distribution of installed electrical power at different stages of treatment
Source: Instituto Tecnológico de Canarias
Here, it is possible to see the percentage distribution of the daily energy consumption
(kWh/day) at each stage).
25
Study of water treatment and reclaimed plants to apply renewable energies (Canarias – Andalucía).
Project: TECOAGUA (CENIT).
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