Ecosystem shifts: implications for groundwater management

Freshwater ecosystems provide a large number of benefits to society. However, extensive human activities threat the viability of these ecosystems, their habitats, and their dynamics and interactions. One of the main risks facing these systems is the overexploitation of groundwater resources that hinders the survival of several freshwater habitats. In this paper, we study optimal groundwater paths when considering freshwater ecosystems. We contribute to existing groundwater literature by including the possibility of regime shifts in freshwater ecosystems into a groundwater management problem. The health of the freshwater habitat, which depends on the groundwater level, presents a switch in its status that occurs when a critical water level (‘tipping point’) is reached. Our results highlight important differences in optimal extraction paths and optimal groundwater levels compared with traditional models. The outcomes suggest that optimal groundwater withdrawals are non-linear and depend on the critical threshold and the ecosystem’s health function. Our results show that the inclusion of regime shifts in water management calls for a reformulation of water policies to incorporate the structure of ecosystems and their interactions with the habitat

Sustainability of intensive groundwater development: experience in Spain

Intensive aquifer development is common in arid and semiarid countries. The associated economic and social benefits are great, but management is needed and sustainability has to be analysed in the framework of a sound hydrogeological background which includes recharge as a key term. Recharge under natural conditions may greatly differ from the actual value under groundwater exploitation conditions when the aquifer is connected to surface water bodies or evaporation conditions are modified. Actual recharge is not an aquifer property but is variable depending on groundwater abstraction and its pattern, and changes in surface water-groundwater relationships and other circumstances, such as return irrigation flows, leakages, and activities to artificially modify it. Groundwater plays an important role in nature as it sustains spring flow, river base flow, wetlands, and crypto-wetlands, and the related provision of ecological services to mankind. Therefore, developable groundwater resources and their sustainability have to take into account concurrence and the net benefits of capturing it in a given moment and not in other circumstances, and exchanging groundwater-related nature services for the human use of groundwater. The often large storage relative to annual flow of aquifers implies that aquifer development produces effects that may last decades and even affect upcoming human generations. This new dimension, which has economic and sustainability aspects, is not as important for other water resources. Critical flow thresholds have to be considered for groundwater-dependent ecosystems. This is considered from the point of view of water quantity, which is the dominant aspect under arid and semiarid conditions. However, water quality may be as or more important for humans and for nature services, but this needs a separate treatment. The hydrogeological and socio-economic aspects of aquifer behaviour are presented taking into account the experience drawn from some intensively exploited and economically and socially important aquifers, mostly those in La Mancha, in central Spain, but also other intensively exploited Spanish aquifers. Topdown-down administrative decisions to get a given sustainable have resulted in partial failures, but if action is agreed among stakeholders better outcomes could be achieved. Mixed solutions seem the best approach

Hydro-economic modeling with aquifer-river interactions to guide sustainable basin management

Policymakers in arid and semiarid basins face hard choices on water policies needed for adaptation to climate change. Hydro-economic modeling is a state-of-the art approach that can be used to guide the design and implementation of these policies in basins. A major gap in developments of hydro-economic modeling to date has been the weak integration of physically-based representations of water sources and uses such as the interaction between ground and surface water resources, to inform complex basin scale policy choices. This paper presents an integrated hydro-economic modeling framework to address this gap with application to an important and complex river basin in Spain, the Jucar basin, for the assessment of a range of climate change scenarios and policy choices. Results indicate that in absence of adequate policies protecting water resources and natural ecosystems, water users will strategically deplete reservoirs, aquifers and river flows for short-term adaptation to climate change, disregarding the impacts on the environment and future human activities. These impacts can be addressed by implementing sustainable management policies. However, these policies could have disproportionate costs for some stakeholders groups, and their opposition may undermine attempts at sustainable policy. These tradeoffs among water policy choices are important guides to the design of policies aimed at basin-wide adaptation to climate change

Incentivos para una gestión forestal sostenible y refuerzo del papel de los boques como sumideros de CO2

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