Since 1950 DWR has conducted over 250 land use surveys of all or parts of California's 58 counties. Early land use surveys were recorded on paper maps of USGS 7.5' quadrangles. In 1986, DWR began to develop georeferenced digital maps of land use survey data, which are available for download here. Our long-term goal for this program is to survey land use more frequently and efficiently using satellite imagery, high elevation digital imagery, local sources of data, and remote sensing in conjunction with field surveys.
In 1947, the California Legislature requested that an investigation be conducted of the water resources and present and future water needs for all hydrologic regions in the State. Accordingly, DWR and its predecessor agencies began to collect the urban and agricultural land use and water use data that serve as the basis for the computations of current and projected water uses.
DWR began surveying land use in the early 1950's for specific projects and investigations. By the mid 1960's DWR began an ongoing program to perform land use surveys every year. The main emphasis of DWR's land use surveys is the mapping of agricultural land. Over 70 different crops or crop categories are included in our surveys. Irrigation methods and water sources have also been mapped in some, but not all surveys. Urban and native vegetation (undeveloped) areas are mapped but not in the detail of agricultural land.
These land use surveys were performed using aerial photos and, more recently, satellite imagery to define field boundaries. For earlier surveys, DWR staff used U.S.G.S. 7.5' quadrangle maps as base maps for delineating field boundaries and recording land uses. As large format printing of aerial photographs became available, plotted aerial photos were used as field sheets for recording land use attributes. Currently, most of the land use survey data is entered directly into a digital map using geographic information system (GIS) software on a laptop computer. Georeferenced, orthorectified imagery is used as a backdrop, and the land use boundaries are visible on top of the imagery. Department staff visit and visually identify land uses on over 95 percent of the developed agricultural areas within each survey area. A GPS unit is incorporated with the computer, so the user can see their current location on-screen.
After the field work has been completed and the maps have been checked for errors, a digital composite map of the survey area is created from the work of individual surveyors. Using GIS software, digital maps of quads, counties, water districts, and the DWR's hydrologic planning units (Detailed Analysis Units) can be overlaid on the land use data to develop acreage summaries of land use by these areas.
Following is a list (by year) of the land use survey data that are available from this site. Every digital survey has a metadata file which explains more specifically and in more detail how that survey was performed. The shapefile of the land use survey data, the metadata, the land use legend, and an explanation of the land use attributes in the shapefile have been combined into a single zipped file for each survey. Click on the survey area and select "Save" to download the data to your computer.See More