Availability of fresh surface water, salinisation

The availability of fresh ground and surface water is important for agriculture, industry, drinking water and nature. Salinisation of ground and surface water takes place in the coastal area of the Netherlands by intrusion of seawater through the large rivers and salty torment (the flow of salt groundwater up to the surface). It is expected that due to predicted climate change and future sea level rises, salty torment and salt penetration from the sea will increase and the availability of fresh ground and surface water will decrease. This factsheet deals with the availability of fresh surface water. Surface water The surface water in the Dutch coastal area can be salt due to external salinisation (intrusion of seawater via the large rivers and estuaries) and internal salinisation (by salty salt). For the large surface waters in the coastal area such as the rivers, canals, estuaries, lakes and lakes, it can be clearly indicated whether it is sweet (lightly brackish) or salt. This is indicated in the map. However, for the system to rides, watercourses and ditches in polders this is not possible at the moment. The salinity of these smaller surface waters is determined by salty salt (internal salinisation), precipitation surplus and inlet water and therefore salinity can vary greatly locally. Also over time, salinity varies greatly due to daily changes in contributions of precipitation and inlet water. The inlet water comes from the large rivers and is generally sweet. Towards the coast, the salt content in the rivers can increase by seawater intrusion. The national hydrological instrumentation NHI can calculate the salinity of the surface water taking into account the amount of salt, inlet water and precipitation surplus at LSW (local surface waters are subpolder systems and often include multiple gauges within a polder). However, at the moment the latest improvements are being made to the NHI and it is expected that by mid-2015 the mentioned NHI results can be used to determine the salinity of the smaller surface waters. Measurements of the salinity of surface water are available at water boards, but the expected effort is currently too large to make a land-covering map. In this version, it is sufficient to indicate the salinity of the large surface waters as discussed above. In addition, for the high part of the Netherlands (maize field > + 0.5 m NAP), the regional and local surface water is indicated as fresh because it does not involve internal salinisation. For low-Netherlands (mowing field < + 0.5 m NAP), the regional and local surface water may be brackish or salt, and this is further determined by NHI (halfway 2015) and supplemented on the map. An indication of the salinity for these areas can already be obtained by looking at the fresh groundwater availability map. Namely, the probability of internal salinisation (by salt torment) is greatest for the areas with a shallow fresh-breaking groundwater interface. Definitions: Chloride is a conservative substance that is relatively high compared to other substances and is the dominant representative of the salt content of water. Definitions of sweet, brackish and salt water are therefore based on chloride concentration. Class — Chloride concentration (mg Cl/L) Sweet < 1000 Broke 1000-3000 Salt > 3000