Quantifying Groundwater Discharge and Streambed Heat Flux in Fortune Creek, British Columbia, Using Time Series of Streambed Temperature Profiles
Time series of streambed temperature profiles and hydraulic head measurements in piezometers were used to characterize groundwater discharge to a small salmonid stream in the interior of British Columbia. Of particular interest was the heat flux into and out of the streamed resulting from groundwater discharge, in light of providing cool water habitat for salmonid species. The larger study objectives were to link salmonid habitat use to habitat quality, including water temperature. Over the summer of 2008, streambed temperature profiles were collected at eight locations along the stream and in two piezometers in a known groundwater upwelling area. Water levels were recorded continuously in the piezometers. Streambed temperature profiles were used in an analytical solution of the one dimensional groundwater and heat flow equation to estimate groundwater flux into and out of the stream. In addition, a time- series analytical model was used to quantify groundwater and heat flux throughout the low flow season using transient temperature profile data. Groundwater flux estimates derived from the models were compared to flux estimates derived from head measurements and slug testing of the piezometers. Heat flux estimates from groundwater were incorporated into an energy balance model assessing the cooling effect of groundwater discharge on stream temperatures.
Applying hillslope-storage models to simulate low streamflow at a watershed scale
Abstract In a recent study Matonse and Kroll (2009) applied kinematic wave hillslope-storage (kw) and hillslope-storage Boussinesq (hsB) models to M8, a small steep headwater catchment that is part of the Maimai watersheds in New Zealand, to estimate low streamflow series and statistics at a watershed scale. Though hillslope partitions with variable parameters lead to improvements in model performance, the kw and hsB models performed similarly when applied to M8, as was expected given the steep slopes of this catchment. These results were constrained by the amount of available data and the size of the study area. This present paper extends this analysis for two larger North Carolina watersheds, the Linville River near Nebo (LRN) and Indian Creek near Laboratory (ICL). These watersheds are both located within the Piedmont physiographic region in North Carolina and have similar size, but their average slope is different, thus providing a good setting to further compare the kw and hsB models. In addition, both watersheds are NWS MOPEX sites, and thus are rich and consistent in data quality and length. These models are coupled with the NWS's SAC-SMA model and compared based on their ability to predict lower streamflow envelopes and low streamflow statistics. With both sites partitioned into multiple hillslopes, the impact of varying average slope is explored. Our results confirm findings from previous studies that have indicated that for relatively steep hillslopes the kw and hsB models will perform similarly. For more shallow hillslopes the kw model represents a good approximation to the hsB model, indicating some flexibility in the kw model even in shallow sloped watersheds. Calibration with the lower 20 and 50 percent of data (as opposed to the full streamflow hydrograph) resulted in models that better simulate low flow statistics, indicating that having additional high flow data impairs a model's ability to reproduce low streamflows.
Examination of Groundwater-Surface Water Interaction at Different Scales
Hyporheic exchange varies spatially as a result of the heterogeneity of aquifer and streambed properties. These flux patterns can be examined at a variety of scales, with the majority of recent studies focusing on reach scale investigations in order to obtain high-resolution measurements in a costly and time efficient manner. Understanding the processes occurring within the hyporheic zone should provide a step toward understanding the linkage between stream-basin dynamics. A field scale investigation of groundwater surface water interactions is currently underway in Nova Scotia, Canada using a variety of techniques including the deployment of temperature and level loggers within the stream, streambed, and monitoring wells at various locations in the watershed. Current efforts involve trying to rectify different estimates of groundwater discharge arrived at through hyporheic zone measurements, hydrograph separation and groundwater modeling at the aquifer-scale.
An Examination of the Effect of Changing Recharge Rates on Coastal Aquifers
Saltwater intrusion along coastlines has been a serious problem in several areas in North America and around the world. With sea level rising every year, saltwater intrusion is becoming a prominent problem in coastal aquifer sustainability. It is suspected that coastal groundwater supplies in Nova Scotia have the potential for saltwater intrusion, but this possibility has not been clearly defined or studied. It is also unclear what effect changes in the recharge rates will have on the distribution of saline groundwater. In this study, predictions of future salinity distributions are made with numerical models using probable future sea levels and groundwater recharge rates.