Water regulation subsurface

This map gives an overview of promising measures, spread across the Netherlands, to exploit the storage capacity of the subsurface. The storage capacity for water in the subsurface offers many possibilities, both for freshwater supply during dry periods and for catching precipitation and high water peaks. In both cases, the subsurface acts as a buffer to absorb and reduce the effect of extreme climatic conditions. The ecosystem service that the subsurface provides is in this case the preservation of area-owned water in upstream areas. This is also called mountains at the source. For periods of drought, the use of storage capacity offers opportunities for freshwater supply, as the salvaged water remains available for a longer period of time, both for abstraction (drinking water, irrigation water, process water), as well as through groundwater flow. The latter leads to a more constant feeding of wet (welfare) nature reserves. For a selection of seven water-regulating measures (from the Fresh Water Options Optimzer; Van Bakel et al., 2014) mapped the inlfeed of the physical properties of the subsurface. An 8th measure was added later (see below in the explanatory memorandum) These are the following measures: (1) drains2buffer — construction of deeper, regeblare drains in areas with thin rainwater lenses in salty torment areas with the aim of thickening the freshwater lens. (2) Adjustable drainage — replace traditional drainage with adjustable and/or climate adaptive drainage. (3) creekrug infiltration — increase groundwater level by active infiltration via drains. (4) Freshmaker — injection of fresh water into salty aquifers through horizontal wells. In times of scarcity, the fresh water is recovered. Injection (at 5-10 m depth) is combined with abstraction of salt water at a slightly larger depth (15-20 m) to keep the freshwater bubble in place. (5) vertical ASR — Aquifer Storage and recovery — injection of freshwater during periods of surplus through a vertical well and abstraction of the same water through the same well in times of scarcity. (6) water conservation through the construction of weirs that increase both surface water and groundwater level. (7) water conservation by ditch bottom increase (Figure 1) which increases the drainage base (8) MAR — Managed Aquifer Recharge — active infiltration in case of surplus; recovery through pumps or natural roads below currents as feed for stream systems and other wet nature areas.