Hydrologic Budget Assessment of a Small Forested Lake in Northwestern NJ

Sara Kelly (California State University, Monterey Bay), Diana Flores (Montclair State University), Jonathan Jordan (University of California, Riverside) & Amber Lutey (Lehigh University)

Faculty Mentors: Kirk Barrett, Josh Galster & Duke Ophori (Montclair State University)

Lake Wapalanne is a manmade lake, approximately 5.4 hectares, fed primarily by a small stream, with controlled outflow at a broad-crested weir. Located at the eastern edge of the Appalachian Ridge and Valley physiographic province in northwestern New Jersey, Lake Wapalanne and its watershed lie within a forested landscape, surrounded by 6500 hectares of protected land. The lake’s location, small size, simplified inflow and outflow, and minimal external impacts provide a research environment ideal for studying present and future hydrologic lake dynamics. Quantifying the water budget for this small lake improves upon the existing understanding of regional surface water and groundwater interactions. Between July 13th and August 3rd we developed a hydrologic budget for Lake Wapalanne. We quantified precipitation, evapotranspiration, stream inflow and outflow, groundwater seepage, and lake water storage using direct and indirect methods. We installed a weather station to collect precipitation, evapotranspiration, and additional weather data used to calculate evaporation with the Penman-Shuttleworth equation. To develop a rating record between water depth and stream discharge, we installed water level loggers at the inlet and outlet streams and within the lake. To determine inlet and outlet discharge rates we used the midpoint method at 60% depth to measure velocity; we used a broad-crested weir equation to verify the outlet stream discharge. We measured groundwater using seepage meters and piezometers installed at various locations in the lake. To determine changes in lake water storage, we completed a bathymetry survey using a total station and used ArcGIS spatial analyst software to create relationships between depth, area, and volume. The water budget was computed in Excel with all variables quantified on a 15-minute interval. Our initial results indicate that the average total precipitation and evapotranspiration were 0.2 cm/day and 0.4 cm/day respectively. For a more detailed report of lake evaporation see Jordan et al. 2011, this conference. Inflow and outflow discharges were 1290 and 2350 m3/day respectively, or, expressed as an equivalent depth over the lake's surface area, 2.4 and 4.3 cm/day. The change in lake storage was minimal. Interpolated groundwater discharge into the lake was 2.4 cm/day; however, preliminary groundwater results indicate lake water is seeping into the ground. Additional groundwater data and quantification of overland flow is necessary to refine the hydrologic budget for Lake Wapalanne. This study is part of an ongoing NSF Research Experience for Undergraduates (REU) project that encompasses additional topics of lake research, including algal, phosphorous and sediment analyses. These results and methods create a baseline water budget for future efforts to use and expand upon, and have water resource implications as nearby lakes and reservoirs provide drinking water to over five million people.

  • Presented at the 2011 Fall Meeting of the American Geophysical Union (AGU), on December 5-8, 2011 at San Francisco, CA.