Northern valleys aquifers – Siskiyou County groundwater basins underly remote, economically disadvantaged rural intermontane regions with three managed groundwater basins (Scott, Shasta, and Butte Valleys) used predominantly for irrigation of pasture and forage crops (alfalfa). The groundwater (GW) basins are small relative to their respective upland watersheds. GW pumping is less than half of watershed runoff. But in Mediterranean climate, baseflow in summer is critically affected by both pumping and climate change. Siskiyou County has recently begun GW sustainability planning
Yolo County’s aquifer, in California’s Northern Central Valley, mostly serves extensive agriculture. It is managed by the Yolo Subbasin Groundwater Agency, a consortium of local agencies including cities and irrigation systems. Most are managed and priced to encourage conjunctive use, which has resulted in decades of non-depletion of the aquifer. This is an example of successful long-term management with minimal state regulation and without depletion, although some problems and long-term threats remain.
The Tulare Lake Basin aquifer, in California’s southern Central Valley, also mostly serves agriculture. This basin is much larger, drier, and institutionally diverse, with the greatest GW overdraft and depletion in California, over 100 billion cubic meters of overdraft accumulating in the last century. The region supports more than a million hectares of irrigated agriculture, and 2 million residents, and has California’s greatest water-use per unit area. The region has little precipitation and runoff, which is heavily managed, and imports substantial amounts of water from the San Joaquin River and the Sacramento-San Joaquin Delta to the north (now subject to increasing environmental limitations). GW is managed by over 30 local GW sustainability agencies (cities, counties, irrigation and water districts) overlying six GW sub-basins.
The Seudre basin covers an area of 750 km². Its hydrology is highly dependent from GW (karstified limestone aquifer). The downstream part of the basin hosts numerous wetlands, marshes and brackish lagoons which also depend from river flows and GW levels. These groundwater dependent ecosystems sustain significant activity in particular high quality oyster production (Marenne Oléron brand). The hydrology is heavily modified due to the presence of a network of drainage and irrigation canals, and weirs maintaining water levels in marshes and lagoons. One of the contribution of the INCLUSIVE project will consist in untangling the complexity of the basin, with a focus on understanding the contribution of GW. The research will be conducted in close cooperation with the Syndicat Mixte du Bassin de la Seudre, in charge of water management and planning.
Deep confined aquifers of Adour basin
Deep confined aquifers of the Adour basin. This complex multilayer aquifer extends over 4 counties in South-West France, at depth varying from a few meters to 800 m. The resource is mainly exploited for drinking water (70% of extractions) and more marginally by agriculture (11%) as well as by the spa industry (13%). The aquifer is also used as a reservoir for storing natural gas in summer, generating fluctuations in GW levels and triggering tensions between the water and energy sectors. Over the last 20 years, GW levels have been declining by 60 cm per year on average. This has impacted the functioning of thermal springs and reduced the productivity of wells used for drinking water supply. In the last 10 years, the State has promoted (without success) the establishment of a stakeholder platform to develop a sustainable GW management plan. INCLUSIVE will contribute to this endeavor by testing innovative participatory approaches, in close collaboration with Institution Adour.
Born & Buch lakes basin
Born, Buch and lake basins. This case study corresponds to the basin of two small coastal rivers (Born & Buch) extending over 1490 km² and including two large lakes (1 of which is identified as strategic water supply resource for the future), many wetlands, and coastal waters used for oyster production. The hydrology of the basin is greatly influenced by shallow GW as well as by forestry (main land use) and irrigated agriculture. A water management plan has already been developed by a local water commission involving all key stakeholders. The Local Commission is currently working on adaptation to climate change, with the support of the Syndicat Mixte du Basin Versant des Lacs du Born (see letter of support). Major issues include GW overexploitation in summer, deterioration of water quality in lakes (linked to reduced GW inflow), decreasing river base flows. INCLUSIVE will contribute to the development of a climate change adaptation strategy, considering all interactions that exist between rivers, lakes, wetlands, GW, coastal water, forestry and agriculture, as well as the links between water quality and quantity issues.
Ob-Irtysh river basin. The case study covers the closed drainage area of the Ob-Irtysh river basin with a total area of more than 170 000 km2. All flowing rivers are used only for agricultural water supply and irrigation. For drinking water needs and partly for irrigation purposes, GW resources are used. To secure water supply and ensure quality of drinking water, deep wells were drilled (200-300 m and more – up to 1.5 km). Despite different preventive measures undertaken to tackle the problem of water supply in the basin, the issue still remains unsolved and is in need of development of a regional level model for water resources management, to achieve a rational and sustainable use of the resource while using less financial resources. The situation is complicated by the fact that these territories had a long history of agricultural development, and present issues such as salinization, soil degradation, agricultural pollutants, etc. The INCLUSIVE project will take into account the interrelations in the soil-GW-water users system and in particular will develop a geochemical salt migration model which will support strategic decision making at a regional level.
Choshui River alluvial
The Choshui River alluvial fan is located on the mid-western coast of Taiwan, and covers the fertile plain area of 1800 km2 including counties of Yun-Lin, Chang-Hua, and northern Chia-Yi. This multilayer aquifer is used for agricultural irrigation (80%), drinking water supply (11%) and industry (9%). The resource is overexploited due to lack of control of illegal wells (used for aquaculture, agriculture and domestic uses), resulting in GW depletion and land subsidence, which in turns impact major transport infrastructure an accentuate flood problems. From a management perspective, there is an urgent need to design acceptable rules for regulating GW extraction and to develop a plan for conjunctive ground-surface water management. The INCLUSIVE project will contribute to that objective, in close cooperation with the Water Resource Agency and with Yunlin and Changhua Irrigation Associations, whose role have recently been strengthened.