Projects and Programs

Field Characterization and Numerical Simulation of Ground-Water and Surface-Water Interactions in Rhode Island Wetlands: Big River Watershed Case Study

2008

2012

Big River Watershed, Rhode Island

Rhode Island Water Resources Board and U.S. Geological Survey

Robert Breault

Robert Breault, Jason Sorenson, Gregory Granato, and John Masterson

Water demand in Rhode Island is increasing, and the Rhode Island Water Resources Board (RIWRB), which is responsible developing and protecting the State’s major water resources, is concerned that this increasing demand may exceed the current capacity. Nearly all of the potable ground-water supplies identified in Rhode Island are found in shallow, river-dominated valley-fill aquifer systems, such as the Big River Watershed in central Rhode Island. There are concerns about potential effects of ground-water withdrawals on the hydrology of streams and wetlands. These concerns have created the need for a better understanding of the interaction between ground water and surface water in wetlands in order to better assess potential effects of pumping on wetlands. The RIWRB has determined that there are no established methods to address these concerns in Rhode Island. The RIWRB also has determined that such methods may help water suppliers throughout Rhode Island address concerns of potential effects on the hydrology of wetlands.

The RIWRB in conjunction with the USGS has selected the Big River area as a case study to examine potential field-monitoring and ground-water modeling methods for hydrologic wetland-assessments. The Big River area has been selected because (1) it has been designated as a water-supply protection area; (2) it is currently slated for ground-water development; (3) it has been well characterized by intensive field efforts and modeling studies; and most of the Big River water-supply protection area will not be affected by withdrawals. Therefore, development of a case study in the Big River water-supply protection area presents the opportunity to develop methods for estimating potential effects of withdrawals and the potential for future monitoring in wetlands near the planned water development sites and control sites in areas that will remain in a natural state.

In 1995 the RIWRB and the USGS began conducting a series of scientific investigations in the Big River Watershed in an effort to better understand the hydrogeology and ground-water-development options in this area. Four reports have been published from these investigations: the first report documented the hydrogeologic data collection effort from July 1996 through October 1998 (Craft, 2001); the second report described the geologic setting and aquifer properties of the glacial sediments, including the six aquifer tests conducted in this area (Craft, 2001; Stone and Dickerman, 2002); the third report described the development and simulations of a numerical model for this area to analyze the effects of selected ground-water development options on streamflow (Granato and others, 2003); and the fourth report describes the optimization techniques used to evaluate the potential effects of instream-flow criteria and water-supply demands on ground-water development options and resultant streamflow depletions in the Big River area (Granato and Barlow, 2005).

Although the Big River Basin has been the focus of several scientific investigations, the primary focus of these studies was to assess the potential effects of water-supply development on stream flow. The aquifer tests conducted as part of the initial hydrologeologic investigation (Craft, 2001) were designed specifically to determine the hydraulic properties of the aquifer, rather than any potential impacts on nearby surface-water bodies and wetlands from extended periods of pumping. Also, it can be assumed that the effect of pumping during the two-day tests conducted in that investigation would not propagate to the nearby wetlands during the testing period. As the RIWRB moves forward in pursuing future supply options in this area, a better understanding of the hydrologic response of wetlands to the potential effects of ground-water withdrawals is now needed.

Although potential effects of withdrawals on wetland hydrology were beyond the scope of the original Big River study, the numerical simulations previously conducted with the model of the Big River Watershed represented the wetlands indirectly by simulating the wetlands as areas of enhanced evapotranspiration in order to account for potential streamflow loses not associated with pumping. The hydraulic properties of the wetlands and the hydraulic connection between these wetlands and the underlying aquifer can not be adequately represented with this regional-scale model. Furthermore, the regional model grid with model cells that are 200 feet by 200 feet (about an acre) may not adequately represent small-scale changes in water levels within the area in close proximity to the production-well sites. Therefore, a better understanding of these wetland characteristics and more focused local-scale modeling analyses would be required to better assess possible impacts on wetlands from proposed ground-water development scenarios in the Big River Watershed.

The objective of this proposed USGS investigation is to examine field methods and subregional modeling techniques necessary to improve the understanding of the interaction between ground water and surface water in wetland systems commonly found throughout Rhode Island. Efforts to develop data collection and modeling methods will focus on the Big River water-supply protection area, which is under the jurisdiction of the RIWRB. This investigation will include a focused field effort to test methods for characterizing the hydrology of wetland areas by examining sediments; measuring the hydraulic connection between the wetlands and the underlying aquifer at a reference site and at sites in the ground-water development area analyzed in Granato and Barlow (2005) within the Big River water-supply protection area. A subregional ground-water-flow model also will be developed from the existing Big River model (Granato and others, 2003) to better represent the wetland characteristics determined from the proposed field effort in order to focus on the potential effects of pumping on the wetlands in the Big River watershed near the proposed pumping sites.

This study will help develop field methods and modeling techniques to improve the understanding of ground- and surface-water interactions under changing stress conditions in wetlands in stream-dominated valley-fill aquifers, commonly found through the glaciated regions of northeastern United States. The study supports the RIWRB in its mission for supporting the proper development, protection, conservation and use of the state's water resources while balancing economic development and environmental protection for the State of Rhode Island (http://www.wrb.state.ri.us/). As such, the study will enhance the understanding of the water resources in the Big River water-supply protection area, an important potential regional water supply in the State of Rhode Island.

The proposed investigation also is consistent with the mission of the USGS, as outlined recently in the USGS Strategic Plan: “programs will focus on understanding, modeling, and predicting in an integrated manner how multiple forces affect natural systems. This knowledge will enable land managers, decision-makers, and citizens to make sound decisions about how to live on and manage the land” (http://www.usgs.gov/science_strategy/; accessed February 18, 2003).

This project will be comprised of hydrologic data collection and ground-water-flow modeling components and include the following: (1) use of existing USGS flow model to determine wetland areas that fall within the simulated one-foot drawdown for August pumping and recharge conditions, (2) consultation with RIWRB and RIDEM to select candidate wetlands for proposed field investigation, (3) characterization of wetland sediment thickness and lithologic composition, (4) determination of hydraulic connection between wetlands and the underlying aquifer, (5) development of a subregional ground-water-flow model, and (6) simulation of selected ground-water development scenarios to minimize impacts to wetlands.

The final product of the study will be a USGS Scientific Investigations Report that documents the data-collection effort and the development and analysis of the subregional ground-water-flow model. Interim products will include: a data report; a web-based fact sheet discussing the purpose and approach of the project; and monthly progress reports. A project web-site will be maintained throughout the project which will at a minimum, contain the afore-mentioned interim products. Additionally, average water-level data collected as part of the project will be published in the MA-RI Water Science Center Annual Data Report.

Breault, R.F., Durant, J.L., and Robbat, Albert, Jr., 2006, Sediment quality of lakes, rivers, and estuaries in the Mystic River Basin, eastern Massachusetts, 2001–03: U.S. Geological Survey Scientific Investigations Report 2005-5191, 110 p.

Brooks, R. T. 2005. A review of basin morphology and pool hydrology of isolated ponded wetlands: implications for seasonal forest pools of the northeastern United States: Wetlands Ecology and Management vol. 13, p. 335-348.

Brooks, R.T. 2004. Weather-related effects on woodland vernal pool hydrology and hydroperiod: Wetlands vol. 24, p. 104-114.

Brooks, R.T. 2000. Annual and seasonal variation and the effects of hydroperiod on benthic macroinvertebrates of seasonal forest ponds in central Massachusetts, USA: Wetlands vol. 20, p. 104-114.

Brooks, R.T., and M. Hayashi. 2002. Depth-area-volume and hydroperiod relationships of ephemeral ("vernal") forest pools in southern New England: Wetlands vol. 22, p. 247-255.

Coon, W. F., 1997, Hydrology, sedimentology, and biology of Ellison Park wetland at the mouth of Irondequoit Creek near Rochester, New York: U.S. Geological Survey Water-Resources Investigations Report 96-4269, 41 p.

Craft, P.A., 2001, Hydrologic data for the Big River -- Mishnock River stream-aquifer system, central Rhode Island: U.S. Geological Survey Open-File Report 01-250, 104 p., 1 pl.

Friesz, P.J., 2004, Delineation of areas contributing recharge to selected public-supply wells in glacial valley-fill and wetland settings, Rhode Island: U.S. Geological Survey Scientific Investigations Report 2004-5070, 57 p.

Granato, G.E., Barlow, P.M., and Dickerman, D.C., 2003, Hydrogeology and Simulated Effects of Ground-Water Withdrawals in the Big River Area, Rhode Island: U.S. Geological Survey Water-Resources Investigations Report 03-4222, 76 p.

Granato, G.E., and Barlow, P.M., 2005, Effects of alternative instream-flow criteria and water-supply demands on ground-water development options in the Big River Area, Rhode Island: U.S. Geological Survey Scientific Investigations Report 2004-5301, 110 p.

Skidds, D.E., and F.C. Golet. 2005.  Estimating Hydroperiod Suitability for Breeding Amphibians in Southern Rhode Island Seasonal Forest Ponds:  Wetlands Ecology and Management 13:349-366.

Stone, J.R., and Dickerman, D.C., 2002, Glacial Geology and Aquifer Characteristics of the Big River Area, Central Rhode Island: U.S. Geological Survey Water-Resources Investigations Report 01-4169, 12 p., 1 pl.

Wayne Sonntag, Director, USGS MA-RI Water Science Center (508-490-5002)