Background
The Paso Robles Groundwater Basin study was conducted to provide the San Luis Obispo County Public Works Department, North County public water agencies, and overlying landowners and water users an understanding of the basin by calculating:

• Extent of the basin, laterally and vertically,
• Existence of subbasins and other internal basin structures,
  
• Quantity of groundwater in storage in the basin,
• Hydraulic movement of groundwater through the basin,
• Sources and volumes of natural recharge,
• Perennial yield, and
• Trends in water quality.

This study provided insight into understanding the long-term yield and production capability of this most valuable resource and the foundation that the community needs to eventually participate in water resource planning. The knowledge gained by this study, and access to the data generated by the study, was necessary for the community to develop a confident and consensus based decision-making process.

Fugro's Role
Fugro's role in the project was to collect and analyze existing data for the Paso Robles Groundwater Basin and vicinity. The results of the analysis were then used to create a three-dimensional hydrologic model of the basin. Data was collected in various formats from various sources and was compiled in Fugro's Geographic Information System (GIS). The GIS data is in a form compatible with the anticipated format for a groundwater model. Fugro collected the following types of data:

• Cultural and geographic features including city, county, and state boundaries, roads/highways, coast line, lakes, and rivers/streams,
• Land use features such as phreatophytes and riparian vegetation,
• Aerial photographs,
• Geology and topography,
• Well log data such as water well completion reports, oil and gas well logs, geophysical electric logs, and water level data,
• Hydrologic data such as precipitation records and stream flow,
• Water quality data,
• Water usage data such as agricultural water demand, municipal and community water demand, and rural domestic water demand,
• Water well pumping tests.

Fugro's analysis of the data included:

• Evaluating precipitation data to determine a hydrologic base period from 1980 through 1997,
• Contouring groundwater level surfaces for each year of the base period,
• Calculating the changes in the volume of groundwater storage for the basin for several time periods,
• Mapping the distribution of various water quality constituents,
• Mapping the direction and quantity of groundwater flow through the basin,
• Calculating the basin water balance (hydrologic budget) by estimating basin inflow and outflow components,
• Estimating perennial yield for the groundwater basin and subbasins.