Geohydrologic Characterization, S Water-Chemistry, and Hydrologic P u b r e Model of the Petaluma Valley j e l i c m t Watershed, Sonoma County, CA i t n o a R r y e Tracy Nishikawa, D.S. Sweetkind, N.F. Teague, v i and Jonathan Traum s i o 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
Petaluma Valley Watershed S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Approach: 4 Tasks · Geohydrologic characterization · Data collection/interpretation: Primarily water S P u b r quality e j e l · Hydrologic model i c m t i t n · Report o a R r y e v i s i o n
Geology and Lithologic Framework Model · Information from previous studies were integrated with digital geologic map, borehole, S and geophysical data to create a three- P u dimensional geologic framework model of the b r e j e Petaluma Valley watershed (PVW) that defines l i c m the subsurface stratigraphic and structural t i t n architecture for the study area. o a R r y · This digital model provides the fundamental e v i geologic framework for the subsequent s i o development of a transient hydrologic model of n the PVW.
Surface Geology S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Wells Used for Geologic Framework Model S P u b r e j e l i c m t i t n o a R r y e v i s i o n
S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Cardwell, 1958 (Spring 1951 Water Levels) S P u b r Petaluma e j e Valley l i c m t i t n o a R r y e v i s i o n
Spring 2010s Water Levels S P u Petaluma b r Valley e j e l i c m t i t n o a R r y e v i s i o n
S P u b r Petaluma e j e Valley l i c m t i t n o a R r y e v i s i o n
Water Quality Constituents · Used previously collected data and new data · Field parameters: Temperature, pH, dissolved S P u oxygen, and specific conductance b r e · Total Dissolved Solids and Major ions: calcium, j e l i c m magnesium, sodium, potassium, chloride, t i t n o sulfate, carbonate, and bicarbonate a · Selected trace elements: nitrate, iron, R r y e v manganese, arsenic, and boron i s · Stable isotope: Isotopes of hydrogen (deuterium) i o n and oxygen-18 · Age dating: hydrogen-3 (tritium) and carbon-14
Water- Quality Sampling S Locations P u b r e j e l i c m t i t n o a R r y e v i s i o n
A-A’ S P u b r e j e l i c m t i t n o a R r y e v i s i o n
B-B’ S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Chlorides S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Nitrate S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Stable Isotopes S P u b r e j e l i c m t i t n o a R r y Franciscan/Tolay Volcanics e v i s i o n W42 W22
Age Dates S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Is Seawater Intrusion Occurring? S P u b r e Freshwater j e l i entering marine c m t sediments i Seawater t n o a entering R r y freshwater e sediments v i s i o n
Petaluma Valley Integrated Hydrologic Model (PVIHM) Overview S P u b r e j Water Supply Climate Hydrogeologic Groundwater Streamflow Landscape e l and Demand Data Data i Data Data Data c m Data t i t n o a R r y e MODFLOW-OWHM v Fully coupled simulation of groundwater flow, surface-water flow, and i landscape processes s i o n Water Groundwater Streamflow Levels Budgets
Major Features of PVIHM · Simulates the groundwater flow, surface-water flow, and landscape processes in the 99,000 acre S Petaluma Valley watershed P u · Simulates 56 years of historical hydrology from b r e j e l 1959 to 2015 i c m · Utilizes data from local, state, and federal t i t n o sources a R r · Incorporates the updated hydrogeologic model y e v to represent the multi-layered aquifer system i · Calibrated using groundwater level from 41 s i o groundwater monitoring wells and measured n streamflow data from 3 USGS streamflow gages
Model Domain and Grid S P u b r e j e l i c m Petaluma t Valley i t n o a R r y e v i s i o n
Average Groundwater Budget S P u b r e j e l i c m t i t n o a R r y e v i s i o n
S P u b r e j e l i c m t i t n o a R r y e v i s i o n End of Simulation - Simulated Groundwater Levels
Model Uses · Understand the hydrologic responses related to conjunctive use of surface water, recycled S P u water, and groundwater b r e · Simulate future conditions under different j e l i c m t hydrologic and water management conditions i t n o · Changes in future climate a R r · Changes in future land use y e v · Different magnitudes, distributions, and timing of i s i city of Petaluma pumping o · Support the development of a Groundwater n Sustainability Plan (GSP)
Future Climate: Wet vs Dry End of Simulation S Wet - Dry P u b r e j e l i c m t i t n o a R r y e v i s i o n
Future Land Use S P u b r e j e l i c m t i t n o a R r y e v i s i o n
Summary and Conclusions · Study area is a modified version of the Petaluma River watershed: Petaluma Valley watershed S P (PVW) u b r · Geohydrology e j e l i c m · Principal aquifer units spatially constrained t i · Data confirms Petaluma Valley fault t n o a · Data indicate the Quaternary mixed unit located along R r y e axis of valley v · Surface-water Hydrology i s i o · Local surface water not important for supply but n affects groundwater quality and supply. · Petaluma River tidally influenced north of downtown
Summary and Conclusions · Groundwater · Found in Wilson Grove, Petaluma, Quaternary, Sonoma S P u Volcanics, and Bay Muds b r · Primary sources: infiltration from precipitation, with e j e l i some stream leakage, boundary inflows, and irrigation- c m t return flow. i t n o · Primary sinks: pumping, evapotranspiration of shallow a R r groundwater, boundary outflow, and baseflow. y e · Groundwater flows from hills toward Petaluma River. v i s Then flows southeast toward San Pablo Bay. Not much i o change over time. n · Hydrographs unchanged with local declines.
Summary and Conclusions · Geochemistry · Confirms precipitation is primary source of S P u recharge b r e j · Seawater intrusion is occurring near San Pablo e l i c m t Bay. Source is high-salinity water from tidally- i t n o a influenced Petaluma River and inflow from San R r y Pablo Bay e v · Age dating indicates that deep groundwater along i s i axis of valley represents groundwater at the end of o n long flowpaths and is old · Nitrates in Wilson Grove formation now less than MCL
Summary and Conclusions · Hydrologic model · Simulates: groundwater, surface water, and S P u landscape processes b r e j · Simulated 1959 to 2015 e l i c m t · Calibrated to measured groundwater levels and i t n o a streamflow R r y · Model uses e v · Hydrologic response to conjunctive-use strategies i s i · Hydrologic response to future: climate, land use, and/or o n pumpage · Support GSP
SGMA Undesirable Results · Storage decline: 1% removed from storage S · Groundwater/surface water: Groundwater P u b r providing baseflow e j e l i · Water-level decline: Mostly flat with some c m t i t n localized declines o a · Seawater intrusion: Primarily near bay, R r y e v although tidally influenced river may be i s affecting wells farther upstream i o · Water-quality degradation: Nitrates improving n · Subsidence: N/A
Suggested Future Work · Conduct a surface water/groundwater interaction study along the tidally influenced reach of the river, focusing on S the area near downtown Petaluma and the Lynch Creek P u confluence and the lower part of the river. b r e · Continue monitoring and collecting groundwater level, j e l i c m groundwater quality, and streamflow data. t · Expand groundwater monitoring network to areas of i t n o a uncertainty such as the Wilson Grove and Santa Rosa R r y Plain boundaries. e · Start collecting data on groundwater production for rural v i s and agricultural use and surface-water diversions from i o local sources used for irrigation. n · Collect crop-related data from local growers to reduce the uncertainty in land-use parameters.
Questions? S P u b r e j e l i c m t i t n o a R r y e v i s i o n
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