Sustainable conjunctive water management model for alleviating water shortage

Seeking a pathway towards a more sustainable human-water relationship by coupled model - From a perspective of socio-hydrology

It is essential to systematically consider social, economic, and natural endowments in managing and allocating water resources. However, few studies have comprehensively quantitatively evaluated the allocation of regional water resources from a socio-hydrology perspective and provided recommendations. To explore this research gap, we have constructed a tightly coupled framework that integrates system dynamics models and optimization algorithms to carry out an innovative redistribution of water resources in Shaanxi Province. The system dynamics model simulation results showed that the error was almost always within 10% over the research period, indicating robust simulation capability and laying a solid foundation for subsequent model coupling. The coupled model achieves convergence in approximately 30 generations by formulating the optimization problem with four individual objectives. Optimizing four objectives concurrently results in convergence around the 150th generation. The optimized Pareto solution sets visually demonstrate the trade-offs between different objectives. In the optimized water allocation schedule, the water consumption in Yulin exhibits a change of 1.22 ×108m3, reflecting the most significant optimization effects on agricultural and domestic water allocation. The results indicated that the comprehensive Gini coefficient typically ranged between 0.2 and 0.3. Over the period from the year 2010-2021, the Gini coefficient exhibited a declining trend, signifying a positive trajectory in water resource allocation throughout the research period and a high level of fairness. The annual total green WF of grain in Weinan was the highest at 14.26 ×108m3, followed by Xianyang at 9.52 ×108m3, and the lowest in Tongchuan at 0.54 ×108m3. The annual average amount of blue WF of grain is the highest in Hanzhong, at 11.33 ×108m3, followed by Weinan at 9.60 ×108m3, and the lowest in Tongchuan at 0.14 ×108m3. The coupled framework proposed in this study exhibits significant innovation, scalability, and practical efficiency. It can inspire future research and decision-making and holds the potential for application in other regions.

Spatiotemporal assessment of sustainable groundwater management using process-based and remote sensing indices: A novel approach

This study aims to develop a process-based method for evaluating groundwater sustainability and use the results in an archetypal analysis to fundamentally frame and understand sustainable development interactions in a river basin scale and sub-basin resolution. This method was applied in the Tashk-Bakhtegan-Maharloo (TBM) basin of Iran between 2003 and 2018; anthropogenic and natural factors were considered. With its 31 aquifers in 27 sub-basins, the TBM basin has repeatedly suffered severe droughts and water shortages over the past half a century, highlighting the importance of sustainable groundwater management. This study quantified anthropogenic and natural factors affecting groundwater dynamics to address sustainability and defined representative and relative indices, including climatological and drought conditions, vegetation cover, land cover, and population, to assess groundwater sustainability (GWS). Relative indices, prepared using measured data and remote sensing analysis, were chosen to explain groundwater-related situations, whereas representative indices, such as groundwater level and total dissolved solids, were used to explain the groundwater situation. GWS was spatially monitored using a couple-indicator trend-line slope comparison method to analyze process-based indices. Then, archetypal interaction patterns and their drivers in the groundwater system were investigated using results from process-based indices analyses results. The results showed that the TBM basin has moved towards unsustainable levels because of drought, increased irrigated croplands, unbalanced development of the sub-basins up- and downstream in the river's path, and over-exploitation of groundwater. These findings indicate that a deeper understanding of groundwater problems and stakeholder associations is required in order to adapt to the changing groundwater conditions.

Groundwater security indicators and their drivers: An assessment made in a region of tropical climate (Paraopeba River basin, Brazil)

Groundwater helps overcoming periods of drought buffering their effects on water supply to people, natural ecosystems and the economy. Following the latest Conference of the Parties (COP27), groundwater research gained renewed impulse because the Parties committed themselves to invest on environmental dimensions of water security related with aquifer characterization and protection. In that context, the purpose of this study was to help providing an integrated assessment to some fundamental issues about groundwater security, summarized as the three "how"s: how much, how ready and for how long can groundwater be delivered from watersheds? A complementary goal was to identify and quantify the role of watershed characteristics controlling these "how"s. The methodology combined hydrologic modeling and GIS and the results for the test site (Paraopeba River basin, Brazil) were: (1) the studied river tributaries mostly drain regolith aquifers with short hydrologic turnover times (1.3-23.7 yr) and small aquifer mobile storages (0.1-1.3 m), but high specific yields (0.2-8.2 m/yr), being generally prone to hydrologic droughts; (2) the specific discharge is primarily elevation controlled (via precipitation increases with altitude), but relates positively with drainage density as well; (3) the mobile storage in the Quadrilátero-Ferrífero mountain is larger than elsewhere, being influenced by a local geomorphologic setting (higher coverage with concave hillslopes); (4) the groundwater contribution to streamflow discharge is high (> 50 %, on average), being improved with the coverage of argisols; (5) vulnerability to droughts could be alleviated through expansion of water-retention infrastructure in specific regions, as well as through land use conversions targeting reduced evapotranspiration or sustainable land management of argisol and concave surface landscapes. Although applied to a specific catchment, our results stand on a site-independent methodological framework. Thus, the understanding about groundwater security gained with this study can be inspiring to other workers dealing with tropical climate landscapes.

The COP27 screened through the lens of global water security

Water security is an expression of resilience. In the recent past, scientists and public organizations have built considerable work around this concept launched in 2013 by the United Nations as "the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability". In the 27th Conference of the Parties (COP27), held in Sharm El-Sheikh (Egypt) in last November, water security was considered a priority in the climate agenda, especially in the adaption and loss and damage axes. This discussion paper represents the authors' opinion about how the conference coped with water security and what challenges remain to attend. As discussion paper, it had the purpose to stimulate further discussion in a broader scientific forum.

Rainwater harvesting and water balance simulation-optimization scheme to plan sustainable second crop in small rain-fed systems

Environmental degradation in the form of water shortage and uncertainty has severely affected the food systems across the globe. Especially in India, which is dominated by rain-fed farmers, the need for sustainable water resource and its management at farm level is imperative for farming livelihoods and food security of the country. Rainwater harvesting in on-farm reservoirs (OFR) can enable crop diversification, year round cropping and seasonal vegetable cultivation in rain-fed farming systems in India. However appropriate sizing of OFR remains a serious concern especially for small and marginal farmers with limited land holdings. In this study, a novel and comprehensive simulation-optimization model was developed to determine the optimal size and utilization of OFR. The simulation consisted of water balance of soil and OFR using hydrological analysis for last 28 years, through which supplement irrigation needs and, rainwater harvesting potential was estimated. Optimal use of available water in OFR was designed using a multi-stage process wherein the model generated, compared and screened appropriate vegetable plans for Rabi cultivation. The model was simulated for different OFR sizes and the optimal size was chosen based on its economic feasibility. To demonstrate the model, a case study was simulated wherein high supplement irrigation was estimated, indicating a severe limitation in rain-fed farming. A minimum OFR size of 9.9% of the total land was required. With an increase in OFR sizes, the profits increased however, the growth rate declined as the cropping area was reduced. An OFR size of 15.5% of total land was found to be optimal which gave benefit-cost ratio and payback period of 2.4 and 6.8 years respectively. Trends in cultivation plans for different sizes of OFR was observed wherein for small OFR sizes, the model generated fewer options of cultivation plans and preferred crops with high water productivity over crops with high profitability. The proposed model is generic and applicable at multiple scales and scenarios. The model could be used by environmental decision makers, farm managers, policy makers and researchers to determine the feasibility of any water resource intervention using an ecosystem centric approach when multiple scenarios of cultivation are possible.