Miguel of the Calexico New River Committee gave us a great tour of some interesting spots on the New River around Calexico. This river is reported to be heavily polluted as it flows across the international border in the heart of Mexicali/Calexico.
There was a small amount of E.coli indicator in the Alamo river as it flowed across the international border. We found no other E.coli in rivers, irrigation canals, or irrigation drainage ditches except for one canal north of Brawley near Hwy 111 which also had 1 E.coli / ml. Our sampling was by no means a representative sample of irrigation canals or the rivers of Imperial county. We were unable to obtain a sample of the new river. These data suggest that further study would be useful to discover if fecal pollution is indeed a problem in irrigation canals.
If you are interested, email me for a KMZ file or the data.