TOWARDS SUSTAINABILITY: SIMULATING HYDROLOGIC AND BIOLOGIC RESPONSE TO LAND USE AND CLIMATE CHANGE

Hydrologic measurements and models are well-suited for characterizing groundwater and surface water systems, but simple abiotic indicators may not answer the hydroecological questions related to sustainable water use. Thus, understanding how changes in the hydrological system might ripple to the biological system is a critical topic for understanding and protecting groundwater dependent ecosystems – a primary element of sustainable groundwater withdrawals. In this work, the effect on the biotic system was evaluated using simulated changes in hydrograph shape metrics (indices of hydrologic alteration). In this approach, the hydrograph is characterized using several criteria (e.g., low-flow duration, stormflow recurrence), which are then summarized into a set of statistical metrics. Such approaches are promising because change predictions are commonly reported in abiotic terms such as changes in flow, yet societal concerns are often ecosystem focused.

The USGS coupled hydrologic model GSFLOW was used to simulate two watersheds in Wisconsin, USA. Model results were processed using The Nature Conservancy Index of Hydrologic Alteration (IHA) software suite to assess possible biological response to changed streamflow resulting from climate and land-use change. In one watershed the relation established between both macroinvertebrate abundance and richness and the low pulse frequency counts was extrapolated to change scenario conditions. The increased temperature scenarios resulted in decreases in expected invertebrate abundance. In the other watershed, high flow indices changed in response to conversion of Conservation Reserve Program lands to biofuel production – increases augmented by the addition of climate change. Results from both watersheds suggest that hydrographic shape metrics hold promise for helping translate future changes in climate or land use to ecosystem health, and by extension, sustainability.