Water and water quality issues are major concerns for California. In the San Jacinto River Watershed, Lake Elsinore and Canyon Lake were identified by the California Regional Water Quality Control Board (RWQCB) on its Clean Water Act Section 303(d) list as impaired waterbodies. This designation necessitates the development of Total Maximum Daily Loads (TMDLs) of nutrient pollutants causing the impairment. The RWQCB set a timeline for load reductions to meet TMDL compliance by December 31, 2020.
Faced with this challenge, the Western Riverside County Agricultural Coalition (WRCAC) contracted AIS to create a geographic information system cataloging agricultural land uses (AgLU) in the San Jacinto River watershed for 2007. Developing an accurate AgLU database would enable WRCAC to identify existing and potential sources of nutrient flow into water bodies, more readily identify and contact the responsible owners, and enhance future modeling needs.
Following the success of the initial 2007 AgLU project, WRCAC commissioned AIS to conduct two more inventories: past AgLU conditions for the year 2005, and conditions in 2010.
When it was time to assess conditions for 2014, the San Jacinto River Watershed Council (SJRWC) contributed funding which, combined with funding from WRCAC, enabled AIS to produce a comprehensive inventory of all land use types (urban as well as agricultural) within the watershed.
In this latest mapping effort, 2014 National Agriculture Imagery Program (NAIP) aerial imagery served as the basis for land use interpretations. While viewing the orthophotography on screen, AIS staff verified or updated existing land use units, or created new ones. Boundaries for agricultural land uses were reconciled with parcel information where appropriate. The resulting maps were validated during windshield field surveys.
After the database was revised according to the field findings, final quality control and GIS processing steps produced an accurate, seamless land use coverage over the entire watershed.
The resulting dataset helped all stakeholders address water quality issues and continue coordinated efforts to achieve TMDL compliance objectives.