Geohydrologic Characterization, P r e Water-Chemistry, and Hydrologic l i m i u n b Model of the Petaluma Valley a j r e y c t I Watershed, Sonoma County, CA n t o f o R r m e Tracy Nishikawa, D.S. Sweetkind, N.F. Teague, a v t i s i o and Jonathan Traum i o n n - This information is preliminary and is subject to revision. It is being provided to meet the need for timely best science. The information is provided on the condition that neither the U.S. Geological Survey nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information. U.S. Department of the Interior U.S. Geological Survey
Problem Statement · Imported Russian River water primary source of P r water supply to Petaluma Valley e l · However, groundwater is a supplemental source i m i u n of water for the City of Petaluma and is the b a j primary source of supply for agriculture and r e y c domestic use by rural property owners t I n t · Water managers face the challenge of meeting o f o R r m the increasing water demand with a combination e a v of Russian River water, which has uncertainties t i s i o in its future availability, local groundwater i o n n - resources, and recycled wastewater · Petaluma Valley groundwater basin is a SGMA medium-priority basin
Petaluma Valley Groundwater Mgt Questions · What will be the effects of current practices and P r e future groundwater development in the Petaluma l i m Valley? i u n · What are efficient strategies for surface- b a j r e y water/groundwater management that will assure c t I n t the long-term viability of water supply in the o f o R r Petaluma Valley? m e · How can local groundwater resources be utilized a v t i s i o i to help meet the target for local water supplies o n n - during periods of regional water-supply curtailment due to drought or emergency measures?
Petaluma Valley Watershed P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Approach: 4 Tasks · Geohydrologic characterization P r e · Data collection/interpretation: Primarily water l i m i u n quality b a j · Hydrologic model r e y c t I n · Report t o f o R r m e a v t i s i o i o n n -
Geology and Lithologic Framework Model · Information from previous studies was integrated P r with digital geologic map, borehole, and e l i geophysical data to create a three-dimensional m i geologic framework model of the Petaluma u n b a Valley watershed (PVW) that defines the j r e y c subsurface stratigraphic and structural t I n t architecture for the study area. o f o R r m e · This digital model provides the fundamental a v t i s i o geologic framework for the subsequent i o n n - development of a transient hydrologic model of the PVW.
Surface Geology • Faulted P r • 5 primary, areally e l i m constrained i u formations: n b a • j Wilson Grove: fine- r e y c grained marine t I n sandstone t o f • o Petaluma: lacustrine R r m silty/clayey e mudstone a v t • i s i Sonoma Volcanics o i • o n Quaternary n - • Alluvium • Quaternary mixed unit • Bay Muds
Wells Used for Geologic Framework P r e Model l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Cardwell, 1958 (Spring 1951 Water Levels) P r e l i m i u n Petaluma b a Valley j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Spring 2010s Water Levels P r e l i m Petaluma i u n Valley b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
P r e l i m i u n Petaluma b a Valley j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Water Quality Constituents · Used previously collected data and new data P r · Field parameters: Temperature, pH, dissolved e l i m oxygen, and specific conductance i u n · Total Dissolved Solids and Major ions: calcium, b a j r e y c magnesium, sodium, potassium, chloride, t I n t o f sulfate, carbonate, and bicarbonate o R r · Selected nutrients and trace elements: nitrate, m e a v iron, manganese, arsenic, and boron t i s i o i · Stable isotopes: Isotopes of hydrogen o n n - (deuterium) and oxygen-18 · Age dating: hydrogen-3 (tritium) and carbon-14
Water- Quality Sampling P r e Locations l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
A-A’ P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
B-B’ P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Chlorides P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Nitrate P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Stable Isotopes P r e l i m i u n b a j r e y c t I n t o f o R r m e Franciscan/Tolay Volcanics a v t i s i o i o n n - W42 W22
Age Dates P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Is Seawater Intrusion Occurring? P r e l i m i u n Freshwater b a j r e entering marine y c t I sediments n Seawater t o f o entering R r m freshwater e a v sediments t i s i o i o n n -
Major Features of PVIHM · Developed using MODFLOW-OWHM P r · Simulates the groundwater flow, surface-water flow, e l i m and landscape processes in the 99,000 acre Petaluma i u n Valley watershed b a j · Simulates 56 years of historical hydrology from 1959 r e y c t I n to 2015 t o f o · Utilizes data from local, state, and federal sources R r m e · Incorporates the updated hydrogeologic model to a v t i s i o represent the multi-layered aquifer system i o n · Calibrated using groundwater level from 41 n - groundwater monitoring wells and measured streamflow data from 3 USGS streamflow gages
Model Domain and Grid P r e l i m i u n b a j r e y Petaluma c t I Valley n t o f o R r m e a v t i s i o i o n n -
Average Groundwater Budget P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Simulated September 2015 Water Levels P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Model Uses · Understand the hydrologic responses related P r e to conjunctive use of surface water, recycled l i m water, and groundwater i u n · Simulate future conditions under different b a j r e y c hydrologic and water management conditions t I n t o f · Changes in future climate o R r m · Changes in future land use e a v · Different magnitudes, distributions, and timing of t i s i o i o n City of Petaluma pumping n - · Support the development of a Groundwater Sustainability Plan (GSP)
Future Climate: Wet vs Dry P r e End of Simulation l i Wet - Dry m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Future Land Use P r e l i m i u n b a j r e y c t I n t o f o R r m e a v t i s i o i o n n -
Summary and Conclusions · Study area is a modified version of the Petaluma P r e River watershed: Petaluma Valley watershed l i m (PVW) i u n · Geohydrology b a j r e y · Principal aquifer units spatially constrained c t I n · Data confirms Petaluma Valley fault t o f o · Data indicate the Quaternary mixed unit located along R r m e a v axis of valley t i s i · Surface-water Hydrology o i o n n - · Local surface water not important for supply but affects groundwater quality and supply. · Petaluma River tidally influenced north of downtown
Summary and Conclusions · Groundwater P r · Found in Wilson Grove, Petaluma, Quaternary, Sonoma e l i m Volcanics, and Bay Muds i u · Primary sources: infiltration from precipitation, with n b a j r e some stream leakage, boundary inflows, and irrigation- y c t I return flow. n t o f · Primary sinks: pumping, evapotranspiration of shallow o R r m groundwater, boundary outflow, and baseflow. e a v · Groundwater flows from hills toward Petaluma River. t i s i o i Then flows southeast toward San Pablo Bay. Not much o n n - change over time. · Hydrographs unchanged with local declines.
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