1. Sedimentology, Resource Conservation Methods and Environmental Policy of Irrigated Row Crop Agriculture in the Salinas Valley, CA Don Kozlowski May 2001

2. Background 1972, Clean Water Act, Sect. 303(d) list & fix pollution via TMDL Salinas River listed as impacted by sediment Beneficial uses & the Endangered Species Act 2001, still no TMDL for the Salinas Salinas Sediment Study hired by state for technical assistance

3. Possible Sources Agriculture 15% of area is row crop agriculture (165,000 ha) 40% sediment of U.S. rivers from cultivated land ag’s contribution to the Salinas River? Urban/suburban Grazing Viticulture Natural processes Recreational use Mining

4. Objectives Determine: Typical sediment yields from row crop ag fields due to irrigation and storm events during a season Efficiency of a particular best management practice, the water/sediment detention basin

5. Methods Site selection Catchment construction Filtration Recording and analysis

6. Methods (cont’) Create model that predicts field erosion –Determined from various event parameters Upscale the field data to watershed scale –GIS model to get area & slope –Rainfall model For detention basins –Compare sediment into basin to sediment out

7. Results (15 events monitored: 9 irrigation, 6 rainfall) Erosion Analysis (example):

8. Results (cont’) Erosion Model:

9. Still More Results Watershed Scale Erosion Estimates: –Rainfall: 93 kilo-tonnes, 1.2 tonnes/ha –Irrigation: 141 kilo-tonnes, 1.7 tonnes/ha –Total: 234 kilo-tonnes, 2.9 tonnes/ha –60% of agricultural row cropland, slopes <2.3% –Only a fraction of this made it to the Salinas River Efficiency of Detention Basin –100% for sand, at least 99% for silt/clay –211mg/L max outgoing; 46,400 mg/L max incoming CAUTION!!

10. Discussion/Wrap-up Agricultural land use produces a lot of erosion Many BMP’s are in place Detention basins appear to work well Improvements: –Storm erosion dynamics, need more data –Slopes > 2%, need data –Rain model

11. Acknowledgements Farmers SSS team (Thor, Wendi, Adrian, Alana, Bronwyn, Joel, Julie) Mark Angelo, RWQCB Bryan Largay, Monterey Co. RCD NASA/EPA Dr. Sharon Anderson Dr. Lars Pierce Dr. Fred Watson