Calculation of water balance of the weighing lysimeter for assessment of aquifer recharge

Abstract

Ljubljana field aquifer is an important source of drinking water for the Ljubljana city and surrounding areas. Knowledge of the water balance and of the water flow dynamics through the unsaturated zone and recharge of Ljubljana field aquifer is crucial. The water balance assessment of the upper unsaturated zone provides an insight into groundwater recharge and renewal. With the help of build-in monolith weighing lysimeter in Kleče in Ljubljana we have assessed the water balance for hydrological year from March 2014 to February 2015. Water balance parameters, precipitation and evapotranspiration were determined from the changes in the mass of lysimeter and outflow tank. Precipitation events were evaluated based on their duration, intensity and the amount of precipitation. Evapotranspiration and the duration of precipitation were estimated based on the changes of the lysimeter mass. Results show that the chosen period was extremely wet. In the selected hydrological year, precipitation contributed to positive water balance of the upper unsaturated zone, as well as to the recharge of the aquifer.

Keywords

• water balance
• groundwater recharge
• monolithic weighing lysimeter
• Ljubljansko polje
• unsaturated zone