Water Quality Index Score: 64, Marginal
A few key takeaways from our Pueblo Watershed data:
- Chollas River sites often had very high phosphorus and ammonia
- Volunteers found and removed lots of trash from our sampling sites in this watershed
As this watershed is home to Chollas Creek, one of San Diego’s most urban rivers, these results aren’t unexpected. This creek is infamous for drying up, also, so our dataset is missing many samples throughout the year. In fact, more sites went dry this year than any other year in Coastkeeper’s recent sampling history here.
We think all signs point toward poorer water quality than shown with the samples that we could collect, and we wonder with more flow would the Water Quality Index Score have returned a Poor rating?
The high phosphorus and ammonia results belong in the nutrient category, which is common in urban areas with regular use of fertilizers and pesticides on outdoor spaces. An extreme example of this sort of pollution occurred in November, when our volunteer team encountered very black water with a foul odor .
That water sample exceeded healthy standards for nitrate, ammonia, phosphorus, and both types of fecal indicator bacteria. It’s dissolved oxygen was also extremely low. At first, we thought the black water could have been sewage, but an inspector from the city ensured no sewage lines travel to that location. Turns out, it was just really bad water quality. Our guess? Rotting organic matter or some other industrial waste. As indicated in so many of the other watershed data, the low flows and higher-than-normal water temperatures turned Cholla Creek into the perfect breeding ground for rotting vegetation.