Identifying optimal type and locations of natural water retention measures using spatial modeling and cost-benefit analysis

Water management has recently changed from relying purely on technical and engineering methods towards nature-based solutions. These solutions can potentially benefit beyond hydrological concerns, such as improving life quality and biodiversity conservation. These measures are referred to as Natural Water Retention Measures (NWRM) in the water sector. Identifying the optimal type and locations of these measures is challenging due to the abundance of possible solutions, with different potential benefits and varying effects, depending on the characteristics of each place. Most research into sustainable runoff management addresses quantity, quality, and economic issues; few studies link these considerations with environmental and social benefits. We propose a methodology for identifying the most effective areas to place NWRMs and offer criteria for selecting appropriate measures based on hydrological, ecological, and social benefits.

To simulate the effect of NWRM, we applied the Open Nonpoint Source (NPS) Pollution and Erosion Comparison Tool (OpenNSPECT) to simulate the hydrological processes in the Tavor basin. We ran the model multiple times; each time, we simulated increased infiltration in a different land parcel and used the resulting change in runoff, sediment, and pollutants to construct a Pareto frontier graph. We then identified a set of appropriate measures for each area using information from the EU Directorate General for the Environment to conduct a cost-benefit analysis of different water retention measures. Different measures were selected when considering social and ecological benefits than only hydrological benefits, further highlighting the importance of accounting for these aspects. This methodology, which links hydrological concerns with the less commonly found ecological and social aspects, could serve as a decision-making tool for planners and stakeholders with sustainable runoff management.