Land Use Surveys
Since 1950, we have conducted more than 250 land-use surveys of all or parts of California's 58 counties. Early land-use surveys were recorded on U.S. Geological Survey (USGS) 7.5-feet quadrangle paper maps. In 1986, we began to develop georeferenced digital maps of land-use survey data, which are available for download below. 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 Legislature requested 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 collecting the urban and agricultural land-use and water-use data that served as the basis for calculating current and projected water uses.
We first began surveying land use in the early 1950s for specific projects and investigations. By the mid-1960s, we began an ongoing program to conduct land-use surveys every year. The main emphasis of our current land-use surveys is mapping agricultural land. We also collect urban and native vegetation (i.e., undeveloped land) information, but not to the same degree of detail as with agricultural lands. Our surveys include more than 70 different crops or crop categories. Also, some surveys, but not all, have mapped irrigation methods and water sources.
Land-use surveys were originally performed using aerial photos and USGS 7.5-feet 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 information. Currently, most of the land-use survey data are entered directly into a digital map by using geographic information system (GIS) software on a laptop computer. Georeferenced, orthorectified images is used as a backdrop, and the land-use boundaries are visible on top of the images. We visit more than 95 percent of the developed agricultural areas within each survey are and visually identify land uses within them. A global positioning system (GPS) unit is incorporated with the computer, so the user can see their current location onscreen.
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 quadrangles, counties, water districts, and DWR's hydrologic planning units (detailed analysis units) can be overlaid on the land-use data to develop acreage summaries of land use in these areas.
Final Land-Use Data
*For land use maps and data, please visit the link under "Maps."
Land and Water Use Study Areas —Interactive GIS map of downloadable land use survey data.