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Simulation of the upstream effects of Searsville dam and its removal

Christopher Heppner (Stanford University)

Summary

Construction of Searsville Dam in the 1890s created a biotically important lake in a watershed with a high sediment load. Siltation has now reduced the capacity of the lake by about 90 percent. With a grant from the National Science Foundation, PhD student Chris Heppner is studying the effects of Searsville Dam, and its possible removal, on the hydrologic functioning of the upstream area near the lake, including the wetland on the southern end. Hydrologic changes expected to occur after dam removal include a drop in the local water table, decreases in soil saturation near the lake, and changes in evaporation rates, groundwater recharge rates, and interactions between surface water and groundwater. Chris is working with professor Keith Loague. 

Chris's study combines the comprehensive Integrated Hydrology Model (InHM) with a sediment transport model so that he can model streamflow, runoff, and sediment transport through the 14-square mile watershed to Searsville Lake. Chris is tailoring the model with existing data and also new measurements from an array of nine stations (4 within JRBP) where he monitors soil moisture, rainfall, and soil water potential (the pressure necessary to extract water from the soil). One can imagine his model as a mesh draped over the watershed, with the hydrologic processes in each cell interacting with those of neighboring cells. 

Chris's goal is to characterize the hydrologic history of the watershed from the pre-dam period to the present, and then extend the model to predict what would happen if the dam were removed. He will ask questions such as: How quickly will the water table respond to dam removal? When will it stabilize? Over how large an area will changes occur? He will investigate similar questions regarding runoff patterns, evaporation rates, and other hydrologic and geomorphic processes. 

Downstream effects of sedimentation and dam lowering have been examined in other studies (see link)

Left: measuring soil water potential with tensiometer. Right: measuring soil moisture using TDR (time domain reflectometry).

Project Location (Sectors 29, 30, 31, 40)

Visible from Trail/Road

12 - Mapache

13 - Causeway