Modeling river aquifer interactions - Implications for flow restoration
Abstract
The Cosumnes River in Sacramento County, California has historically supported large fall runs of endangered Chinook salmon. Decreasing fish counts over the last 3 decades have been linked to declining fall flows in the river. Severe overdraft of the regional aquifer over the last 60 years has drawn down groundwater levels far below the elevation of the channel over extended reaches of the river, practically eliminating baseflows. Efforts to restore Chinook salmon fall runs have lead to investigations of river aquifer interactions along the lower Cosumnes. Numerical models are being used to guide the development of management strategies to restore fall flows. River aquifer interactions are investigated on a regional (>50km), sub-regional (30km) and a river reach scale (0.2km). Regional groundwater simulations were carried out to quantify regional groundwater deficits with respect to reestablishment of base flows on the Cosumnes River. Results indicated that unrealistic reductions in groundwater pumping would be needed to reconnect the channel with the regional aquifer. Surface flow augmentation and artificial recharge have been proposed as short and long term alternatives to pumping reductions. To evaluate the effectiveness of such measures a sub-regional groundwater model was built. This model is based on detailed geostatistical simulations of the hydrostratigraphy of the alluvial aquifer. Conditional sequential indicator simulations based on transition probabilities and Markov-Chains were used in the geostatistical model. River aquifer interactions are modeled with a finite difference groundwater model including variably saturated flow below the river channel. Riverbed parameterization and calibration of the sub-regional model are supported by reach scale field experiments using piezometers, 3D temperature measurements, automated TDR setups and heat dissipation probes.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....8196F