The water balance and Climate Change in Lelystad
by D. Kuijk
Abstract
The urban area is complex. It consists of buildings, roads, green areas and surface water. The subsurface is just as complex. Interaction between groundwater and drainage, seepage from deeper groundwater aquifers and interaction with surface water make it difficult to determine what is happening. The urban area is also sensitive to damages, both wet and dry conditions can cause nuisance large damages. More insight is needed to simulate the changes in the system under changing conditions of climate and land use. This study has used extensive measurements from two neighborhoods in Lelystad in the period 1968-1984 to calibrate the water balance module in the Drought Stress Model (DSM). The measurements of precipitation, groundwater levels, drainage and sewer discharges have made an accurate calibration of the model possible. This model has allowed for simulation of climate change scenarios, scenarios of changing land use and land cover. Countermeasures to reduce the effects of drought have been simulated to evaluate their efficiency. The simulations showed that the predictions of increased precipitation and potential evaporation in the most extreme scenario cause more evaporation and lower groundwater levels in summer. In winter, the increase in precipitation results in higher groundwater levels. The moderate climate change scenario causes little changes in the urban areas. The increased predicted precipitation leads to more sewer runoff and a rise of the groundwater levels of a several centimeters. The land use changes showed that an increase in paved surface reduces the evaporation from the area. This results in an increase in the other outgoing fluxes, drainage and runoff, as well as an increase in groundwater levels. The counter measures show that both managing the drainage level and using surface irrigation are capable of controlling the groundwater levels. The simulation of the surface irrigation indicated that roughly half of the irrigated water reaches the groundwater. The rest is lost to evaporation.
Student: D. Kuijk
Committee: Dr.ir. Frans van de Ven (TU Delft), Prof. dr. ir. N. C. van de Giesen (TU Delft)