Understanding human-water feedbacks of interventions in agricultural systems with agent based models: a review

Increased variability of the water cycle manifested by climate change is a growing global threat to agriculture with strong implications for food and livelihood security. Thus, there is an urgent need for adaptation in agriculture. Agricultural water management (AWM) interventions, interventions for managing water supply and demand, are extensively promoted and implemented as adaptation measures in multiple development programs globally. Studies assessing these adaptation measures overwhelmingly focus on positive impacts, however, there is a concern that these studies may be biased towards well-managed and successful projects and often miss out on reporting negative externalities. These externalities result from coevolutionary dynamics of human-water systems as AWM interventions impact hydrological flows and their use and adoption is shaped by the societal response. We review the documented externalities of AWM interventions and present a conceptual framework classifying negative externalities linked to water and human systems into negative hydrological externalities and unexpected societal feedbacks. We show that these externalities can lead to long term unsustainable and inequitable outcomes. Understanding how the externalities lead to undesirable outcomes demands rigorous modeling of the feedbacks between human and water systems, for which we discuss the key criteria that such models should meet. Based on these criteria, we showcase that differentiated and limited inclusion of key feedbacks in current water modeling approaches (e.g. hydrological models, hydro-economic, and water resource models) is a critical limitation and bottleneck to understanding and predicting negative externalities of AWM interventions. To account for the key feedback, we find agent-based modeling (ABM) as the method that has the potential to meet the key criteria. Yet there are gaps that need to be addressed in the context of ABM as a tool to unravel the negative externalities of AWM interventions. We carry out a systemic review of ABM application to agricultural systems, capturing how it is currently being applied and identifying the knowledge gaps that need to be bridged to unravel the negative externalities of AWM interventions. We find that ABM has been extensively used to model agricultural systems and, in many cases, the resulting externalities with unsustainable and inequitable outcomes. However, gaps remain in terms of limited use of integrated surface-groundwater hydrological models, inadequate representation of farmers’ behavior with heavy reliance on rational choice or simple heuristics and ignoring heterogeneity of farmers’ characteristics within a population.Water Resource

Impact of high-density managed aquifer recharge implementation on groundwater storage, food production and resilience: A case from Gujarat, India

Study region: The study region is the Kamadhiya catchment (1150 km2), located in the Saurashtra region of the western state of Gujarat, India. The region has seen intensive development of check dams (CDs) for groundwater recharge with an estimated 27,000 CDs constructed up until 2018. Study focus: The impact of CDs on groundwater storage, food production and resilience are assessed for Kamadhiya catchment by estimating and comparing changes, across periods of low and high CD development, in potential recharge from CDs, rainfall trends, and irrigation demand. The analysis is carried out for the period from 1983 to 2015. New hydrological insights for the region: Groundwater storage gains observed following CD development can partly be attributed to an increase in high rainfall years after several drought years. Groundwater demand for irrigation has increased substantially, outweighing increase in groundwater recharge from CDs. This deficit in supply relative to demand is greatest in dry years, and when considered together with the low inter-annual carry-over storage of the region's hardrock aquifers, means that CDs capacity to enhance groundwater storage and mitigate the negative impacts of drought remains limited. Findings suggest that a standalone focus on MAR, unless complemented by greater emphasis on management of water demand and groundwater resources more broadly, may not be sufficient to achieve the long-term goals of sustainable groundwater and concurrently expanding agricultural crop production.Water Resource

Benefits, equity, and sustainability of community rainwater harvesting structures: An assessment based on farm scale social survey

Rainwater harvesting systems (RWHs) are implemented globally to bridge the frequent water supply-demand gaps. This study explores, through farmer household surveys (n = 492), how farmers perceived the benefits of RWHs, the equitability of benefits, and the role of contextual and psychological factors towards the behaviour of maintaining such systems. The study is carried out in a semi-arid catchment in the Indian state of Gujarat where RWHs, in the form of Check dams (CDs), have been implemented extensively. Results show that the benefits of CDs are perceived in good rainfall years through enhanced availability of water for expanding crops and irrigated areas. Farmers reported limited benefits of CDs in dry years. This is because of limited runoff and no carryover of stored groundwater, due to underlying shallow hard rock aquifer with little primary porosity, from wet years to dry years. Overall, ∼ 40%–50% of sampled farmers reported no benefits from CDs and the benefits decreased with distance. This reflects a spatially inequitable distribution of benefits skewed towards the farmers nearest to the CDs. The sustainability of CDs is a challenge with already ∼40% of CDs reportedly not working and 72.8% of farmers reported doing no maintenance activity. This is because 91.2% of farmers reported playing no role in its construction. The results show contextual (participation during construction, economic indicators) and sociopsychological factors (attention to CD condition, maintenance effort) significantly affect the behaviour towards maintaining the CDs. This highlights the need to complement RWHs with wider drought management and water demand management interventions to achieve drought resilience, and adherence to project exit protocols to secure the sustainability of investments.Water Resource