COMPUTING THE HYDROLOGIC BUDGET FOR LAKE WAPALANNE

Between July 13^th and August 3^rd 2011, a hydrologic budget for Lake Wapalanne, New Jersey, was calculated based on the equation, P ± G + S_i – S_o – ET =ΔS. Precipitation, groundwater, stream inflow and outflow, evapotranspiration, and lake water storage were measured using direct and indirect methods. Seepage meters were installed to measure the groundwater inputs and outputs. The stream discharge and the lake depth converted from pressure sensors were used to find the stream inflow and outflow. A weather station measured precipitation and water loss (evapotranspiration). The water budget model (ΔS = P ± G + Si – So – ET) was used to calculate lake storage based on collected and calculated data. A survey of the perimeter of the lake provided lake storage data in addition to the water budget model. Results indicate that the average total precipitation and evapotranspiration were 0.44 cm/day and 0.4 cm/day respectively. Stream inflow and outflow discharges were 2474 m³/day and 4018 m³/day respectively, or, expressed as an equivalent depth over the lake's area of about 5.4 hectares, 4.6 cm/day and 7.4 cm/day. Groundwater discharge out of the lake was 0.6 cm/day. The calculated change in storage was -50,227m³ and the change in storage from the survey was 2,714 m³. The change in lake storage was minimal. Surface water inflow and outflow are the greatest contributors of lake water storage; however, it is believed that water inflow is underestimated in this analysis and is the source for the majority of the error in the hydrologic budget. These results and methods create a baseline water budget for future efforts to use and expand upon research on climate change by providing Lake Wapalanne as model of lake response to climate change.