Effect of land-use change scenarios on nutrients and TSS loads

The projected growth in population in Israel by 50 % by 2030 will greatly enhance urban density and motivate increased urbanization of rural regions in the country. The Lake Kinneret watershed is a rural region of which only about 3 % of the total area is used for residence, and currently, it is the least populated region in Israel. A significant land-use change and growth of urbanized regions is therefore expected in the near future, leading to changes in water quality management in the watershed. In this study, we attempted to quantify the effects of these possible changes in land-use on the flow and pollutant loads discharged from the watershed into Lake Kinneret. To that end, we calibrated and verified the AVGWLF (ArcView (GIS) Generalized Watershed Loading Function) model to simulate stream flows, sediment and nutrient loads under the conditions of a Mediterranean climate watershed. In addition to AVGWLF model, we used two external tools, namely: the HYdrological Model for Karst Environment (HYMKE) to predict daily flows of streams which were not simulated by the AVGWLF model, and a Mediterranean Multiplication Factor (MMF) which was used to improve sediment transport and nutrient load simulations. The combined suite of tools successfully simulated the observed data (r2 > 0.70 and Nash-Sutcliffe efficiency >0.69 for flowrate, sediment and nutrient), including extreme values. The successful combination of the models provides watershed and lake managers the ability to examine the potential land-use changes and their impact on the watershed and the lake downstream.