retention reservoirs in a water-scarce area in
Southern Spain. This study gives evidence that
water harvesting reservoirs can contribute to
reversing desertification and to climate change
mitigation. While the specific system under study
turned out to suffer from ill-informed planning, the
simple modelling approach indicated that permaculture inspired design and planning processes can
facilitate sustainable solutions for integrated soil–
water management. Water harvesting techniques
are a suitable tool for integrated water-soil management and can be attributed to increasing
groundwater levels, soil fertility, and biodiversity.
In view of water-soil-food nexus, this type
of nature-based solutions can be an economically
viable land restoration approach.
Another aspect of the soil–water nexus related
to reservoirs is addressed in the chapter
“Multifunctional Historical data for Improved
Management of Reservoirs” by Sang and Maina
(2021). Sedimentation is a common threat to
reservoirs, in particular in agriculture-dominated
watersheds, but coherent monitoring of sedimentation, let alone sedimentation management
strategies (Hülsmann et al. 2020) are often
lacking, e.g., in Sub-Saharan Africa. Under such
conditions, sedimentation surveys are critical to
assess reservoir volumes and sediment thickness.
The authors review available methodologies for
sediment assessments. Using a bathymetric survey system, which can determine both the
reservoir volume as well as sediment thickness,
the authors investigated two water bodies in
Kenya. In Ruiru Reservoir, which is critical for
the water provision of Nairobi and influenced by
food production in the watershed, a loss of 14%
of its original volume was found. This information can inform the integrated reservoir and
watershed management to secure soils for agriculture as well as maintain water storage capacities and water quality in reservoirs.
The same issue addressed in the chapter by
Sang and Maina (2021), reservoir sedimentation,
is subject to economic evaluation in the chapter
“Economic Valuation of Environmental Services
Associated with Agriculture in the Watershed of
Lake Lagdo, Cameroon”. Yong Ngondjeb and
Ayuk (2021) evaluated the economic impact of
soil erosion, considering current land use management practices and sedimentation of lake
Lagdo in Cameroon, a multi-purpose water body
used also for hydropower. The change in food
production and associated land use practices
increased soil erosion, which influenced lake
sedimentation and led to increasing costs for
electricity generation. This economic impact is
arguably the most tangible one, but clearly not
the only one. Directly or indirectly soil erosion
impacts many other systems, e.g., agricultural
production, which can be prevented by sustainable soil conservation projects. This study
reveals interdependencies between complementary nexus approaches: resource dynamics (water, soil and waste) and sectoral dynamics (water,
food and energy) (Fig. 2).
The next two papers also focus on the waterenergy nexus, both looking in particular from an
economic perspective considering governance. In
the chapter “The Energy-Water Nexus in Iran:
The Political Economy of Energy Subsidies for
Groundwater Pumping”, Jaghdani and Kvartiuk
(2021) analyzed the interlinks between groundwater consumption and government imposed
energy subsidies for the agricultural sector in
Iran. Energy subsidy policies in Iran are threatening the availability of groundwater resources
for irrigation and other uses since they promote
overexploitation. Ultimately, they put agricultural production in the area at risk. Using the
example of a failed political reform in 2010, the
authors argue that the overrepresentation of rural
interests in Iranian politics impeded a successful
reform implementation. The political economy of
energy subsidies can be considered one of the
core topics governing the water-food-energy
nexus in Iran at micro and macro scales.
In the second study on the economics of the
water-energy nexus, Riera and Brümmer (2021)
analyzed the political economy of energy subsidies that influence the groundwater aquifer system in Argentina. In their study “Political
Economy of Energy Subsidies for Groundwater
Irrigation in Mendoza, Argentina”, the policy
tools and scenarios analyzed suggest that there is
a strong link between declining groundwater
resources, grapevine prices, and energy
The Nexus Approach as a Tool for Resources Management …
7
Southern Spain. This study gives evidence that
water harvesting reservoirs can contribute to
reversing desertification and to climate change
mitigation. While the specific system under study
turned out to suffer from ill-informed planning, the
simple modelling approach indicated that permaculture inspired design and planning processes can
facilitate sustainable solutions for integrated soil–
water management. Water harvesting techniques
are a suitable tool for integrated water-soil management and can be attributed to increasing
groundwater levels, soil fertility, and biodiversity.
In view of water-soil-food nexus, this type
of nature-based solutions can be an economically
viable land restoration approach.
Another aspect of the soil–water nexus related
to reservoirs is addressed in the chapter
“Multifunctional Historical data for Improved
Management of Reservoirs” by Sang and Maina
(2021). Sedimentation is a common threat to
reservoirs, in particular in agriculture-dominated
watersheds, but coherent monitoring of sedimentation, let alone sedimentation management
strategies (Hülsmann et al. 2020) are often
lacking, e.g., in Sub-Saharan Africa. Under such
conditions, sedimentation surveys are critical to
assess reservoir volumes and sediment thickness.
The authors review available methodologies for
sediment assessments. Using a bathymetric survey system, which can determine both the
reservoir volume as well as sediment thickness,
the authors investigated two water bodies in
Kenya. In Ruiru Reservoir, which is critical for
the water provision of Nairobi and influenced by
food production in the watershed, a loss of 14%
of its original volume was found. This information can inform the integrated reservoir and
watershed management to secure soils for agriculture as well as maintain water storage capacities and water quality in reservoirs.
The same issue addressed in the chapter by
Sang and Maina (2021), reservoir sedimentation,
is subject to economic evaluation in the chapter
“Economic Valuation of Environmental Services
Associated with Agriculture in the Watershed of
Lake Lagdo, Cameroon”. Yong Ngondjeb and
Ayuk (2021) evaluated the economic impact of
soil erosion, considering current land use management practices and sedimentation of lake
Lagdo in Cameroon, a multi-purpose water body
used also for hydropower. The change in food
production and associated land use practices
increased soil erosion, which influenced lake
sedimentation and led to increasing costs for
electricity generation. This economic impact is
arguably the most tangible one, but clearly not
the only one. Directly or indirectly soil erosion
impacts many other systems, e.g., agricultural
production, which can be prevented by sustainable soil conservation projects. This study
reveals interdependencies between complementary nexus approaches: resource dynamics (water, soil and waste) and sectoral dynamics (water,
food and energy) (Fig. 2).
The next two papers also focus on the waterenergy nexus, both looking in particular from an
economic perspective considering governance. In
the chapter “The Energy-Water Nexus in Iran:
The Political Economy of Energy Subsidies for
Groundwater Pumping”, Jaghdani and Kvartiuk
(2021) analyzed the interlinks between groundwater consumption and government imposed
energy subsidies for the agricultural sector in
Iran. Energy subsidy policies in Iran are threatening the availability of groundwater resources
for irrigation and other uses since they promote
overexploitation. Ultimately, they put agricultural production in the area at risk. Using the
example of a failed political reform in 2010, the
authors argue that the overrepresentation of rural
interests in Iranian politics impeded a successful
reform implementation. The political economy of
energy subsidies can be considered one of the
core topics governing the water-food-energy
nexus in Iran at micro and macro scales.
In the second study on the economics of the
water-energy nexus, Riera and Brümmer (2021)
analyzed the political economy of energy subsidies that influence the groundwater aquifer system in Argentina. In their study “Political
Economy of Energy Subsidies for Groundwater
Irrigation in Mendoza, Argentina”, the policy
tools and scenarios analyzed suggest that there is
a strong link between declining groundwater
resources, grapevine prices, and energy
The Nexus Approach as a Tool for Resources Management …
7