National Research Program (NRP)
The objective of this research is to analyze the impacts of an extended drought on hydrology and biology of a mid-latitude upland watershed. The model outcomes will be used to evaluate the water supply and temperature, and impacts on the fishery habitat.
In 2009, the USGS Office of Groundwater funded the a pilot study to examine the feasibility and utility of widespread use of real-time groundwater monitoring at streambank wells at active streamgages to assist in understanding the exchange of near-stream groundwater and surface water in a cost effective manner (Eddy-Miller et al., 2012). The upgraded sites collected groundwater and stream elevation, and groundwater and stream temperature. Results of this study touched the surface with respect to the multitudes of ways these data, published in a combined manner, can change the way water management is carried out. The combination of data allows an understanding of surface water, groundwater, and how they interact on a landscape-scale. Collected over time, these data will allow a much deeper understanding of climate change, fishery habitat changes, overall stream ecology, as well as give water managers another tool, in both the real-time and long-term to manage the resource. The methodology was proven during the pilot study, and has been lauded by other agencies as critical to the understanding of watersheds. A unified National approach to a new way of collecting and displaying the water resource as one, rather than two separate entities (groundwater and surface water) will allow the USGS to assist with the Interior Secretary’s landscape-scale science strategy.
The general design of an upgraded USGS Groundwater-Streamgage (abbreviated as GW-streamgage) is shown below in Figure 1, depicting the collection of the four primary parameters that defines theses upgraded gages, i.e. 15-minute logging of stream elevation, stream temperature, groundwater elevation and groundwater temperature, with approximately bi-hourly upload of monitored data. (Note that any streamgages collecting less than these specific four defining parameters are not USGS GW-streamgages, but rather standard streamgages collecting other parameters such as stream EC or other water quality parameters). A key element of gw-streamgages stems from USGS WMA developing a series of tools to use heat as a tracer of groundwater movement and stream exchanges with groundwater (Constantz, 2008), such that the value of these upgraded is examined beyond the presence and parameters of water, but its movement as well.
Figure 1: USGS streamgage upgraded to include near-stream groundwater elevation and temperature that is transmitted to the existing gage house via hardwired or radio transmission.
Thus USGS GW-streamgages are capable of monitor the four universally impacted parameters during an extended drought, to examine the onset, continuation and implications of drought in terms of water supply and fishery habitat. This proposal requests funds to simulate the manner in which the stream elevation and near-stream groundwater elevation would trend through an extended drought for a generic mid-latitude upland watershed (a watershed-type indicated as severely impacted by prolonged drought), and qualitatively describe how these changes in water elevation and temperature would alter the stream, such that a cumulative impact on water resources, stream ecology and fisher habitat can be established. As described below, GSFLOW has the ability to simulate this scenario. The EOS article referenced (Constantz and others, 2012) depicts an excellent example of value of GW-streamgages, with a depiction of the annual hydrograph and thermograph from a USGS GW-streamgage on the Big Hole River MT, to track seasonal trends in the four primary parameters.
An integrated hydrologic model called GSFLOW will be used to simulate stream and groundwater head at a location in a hypothetical, snowmelt dominated watershed representative of the Sierra Nevada (i.e., Sagehen watershed; Markstrom et al., 2008). Simulated stream and groundwater heads and flows will provide a synthetic data set for illustrating the type of information that can be provided by the new real-time groundwater and stream gages. GSFLOW simultaneously accounts for climatic conditions, snowmelt processes, runoff across the land surface, variably saturated subsurface flow and storage, plus connections among terrestrial systems, streams, lakes, wetlands, and groundwater. Runoff and interflow (shallow subsurface flow) cascade to receiving streams, while including effects of saturation-excess runoff caused by shallow water table conditions. Accordingly, GSFLOW provides the capabilities to simulate all components of a streamflow hydrograph, SW and GW interactions, and corresponding stream and groundwater heads in response to seasonal snowmelt runoff and groundwater recharge processes (e.g., Huntington and Niswonger, 2012). Furthermore, GSFLOW has been coupled to include in-stream temperature modeling and can provide synthetic stream and groundwater temperature datasets to further illustrate and describe the usefulness of information provided by the real-time groundwater and stream gages (Hunt et al., 2013).