Causes of short term salinity fluctuations of surface water in Noord-Holland

Abstract

Agriculture is affected by climate change, not only due to extreme weather events but also due to sea level rise. Due to this rise, seepage of saline water into polders is enhanced. This influences the availability of fresh water for the use of crop irrigation during droughts. This research aims to use the current available data for the regions Texel, NZG and Oostpolder to predict salinity as a function of precipitation and evaporation. This research shows the results of a project that gathered the electrical conductivity (EC) measurements of surface water in Noord-Holland, the Netherlands. Using a visual analysis, outliers or incorrect data was removed from the gathered EC measurements. The EC data was then used for a time series analysis, using the program Menyanthes, to test if precipitation and evaporation could explain the observed EC values. Precipitation and evaporation data were collected from the KNMI online database. From the analysis one of the conclusions is that the fluctuating EC of a location cannot not be explained by evaporation and precipitation alone. Human interference, such as sprinkling and taking in freshwater into a polder, and saline seepage should also be used as parameters in the time series analysis, but the magnitude of these parameters is not yet known. For this reason it is not possible to make predictions regarding salinity fluctuations of surface water. To make a predictive model possible, the RSGEM model could be used together with a water flow model. In this study it is explained what data and or knowledge is required before a predictive model could be created and used for decision making processes. Additionally, recommendations are made for HHNK using the gained experience during the internship and their vision regarding polder management.