“Nevada County officials have warned people not to swim or use the water in the South Yuba River after it turned yellow Friday,” as The Sacramento Bee is reporting.
“It is unknown what caused the water to turn, but Nevada County officials are saying that the apparent ‘high levels of sediment’ make for potentially unsafe conditions and have issued a no-swim advisory for the river. The affected stretch of river is from Washington to Lake Englebright.
“All people and animals should avoid contact with the water. Samples of the water have been taken, but results will take three to four days to process.”
The rest of the article is here.
Jeff Pelline's Sierra Foothills Report 
The County posted this message on its website last night:
“September 20, 2019 7:03 PM
No Swim Advisory for South Yuba River
The South Yuba River, from below the Town of Washington to Lake Englebright, currently appears to have high level of sediments of unknown origin suspended in the water creating potentially unsafe river conditions for all people and animals. The cause is under investigation, and due to possibly unsafe swimming and recreation conditions, Nevada County Environmental Health has issued a No Swim Advisory for the South Yuba River below Washington to Englebright Lake.
Local officials including Nevada County, South Yuba River Citizen’s League (SYRCL), State Parks, and Nevada County Consolidated Fire District met to discuss current river conditions. Officials from Nevada County Environmental Health went to various South Yuba River locations to take water samples for testing. Full test results will take 3 to 4 days.
With SYRCL’s annual Yuba River Cleanup tomorrow, volunteers are advised to use extra caution to not come into contact with the water and to keep pets away. Some sites may be redirected to alternative areas to protect volunteers from any safety concerns on the South Yuba River. SYRCL’s site leads will be working with volunteers at each of the 35 cleanup locations if redirection to other sites is needed. For questions about SYRCL’s Yuba River Cleanup, please check http://www.yubariver.org.
For updates, visit http://www.MyNevadaCounty.com/YubaRiverAdvisory. Individuals can also call 211 Connecting Point by dialing 2-1-1 or calling 1 (844) 319-4119.”
Yubanet posted this update:
“September 21, 2019 at 1:0 PM Preliminary test results show dangerous levels of E.coli. No Swim Advisory continues for the South Yuba River from the Town of Washington to Englebright, including Englebright Lake.”
Yuck! I wonder if a septic system leaked into the river
No swim advisory lifted: https://yubanet.com/regional/no-swim-advisory-lifted-for-south-yuba-river-and-englebright-lake/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+YubanetRegional+%28YubaNet.com+-+Sierra+Nevada+News%29