Last summer was a tumultuous time for Utah Lake. Low water and associated “toxic” algae blooms sparked headline news and triggered passionate calls to “save the lake.” Concurrently, the State Division of Water Quality is pursuing a program of nutrient removal at wastewater treatment plants (WWTPs). Is this really the solution?
I have studied, taught and researched in environmental engineering and water quality management for many years and directed multidisciplinary water quality studies on many Utah streams and lakes, particularly Utah Lake.
My conclusion: Utah Lake’s water quality and algae growth are not significantly different than in the past, and will likely be the same in the future. Even extreme nutrient removal would not significantly change algae growth and water quality in the lake.
A few facts:
- Utah Lake is very robust and resilient in maintaining relatively good water quality and being a healthy and balanced ecosystem. Why? The lake is shallow, well-mixed, has high oxygen levels and a high pH. These characteristics give the lake good ability to assimilate and stabilize “pollutants.” Many people think the lake’s “muddy” water means it is badly polluted. In fact, its “muddy” nature is not from pollution but from natural mineral particles (precipitates) formed in the lake.
- An abundance of ionic calcium, bicarbonate and silica in the lake, concentrated by a high evaporation rate and fostered by a high pH, precipitates about 100,000 tons/year of sediments. Wave action in this shallow lake suspends these particles; the resulting turbidity markedly limits the light available for algae growth. Clear water would allow growth to the bottom and blooms would explode — resulting in frequent algae “pea soup” conditions across the lake.
- Algae blooms, including cyanobacteria (blue-green) blooms, have always occurred in the lake. During low lake levels, blooms are often heavier and more frequent. Fortunately, most blue-green algae common in Utah Lake produce rather small amounts of toxins.
- Utah Lake has extremely large nutrient inflows, currently 15 to 20 times the amount needed for the algae. However, large nutrient loadings are of little consequence since turbidity appears to be the limiting growth factor for algae, not nutrients.
- Removal of all wastewater phosphorus, along with all possible other sources, would still leave three or four times more phosphorus than needed by the algae. This fact is of tremendous importance. We need to heed what the data tell us, and not buy an ideology that vainly hopes that phosphorus removal is the key to limiting algae growth in the lake — it is not. It’s not wise to fight Mother Nature.
- The futility of trying to make phosphorus limiting to algae growth in many shallow ponds and lakes in this area is further highlighted by noting that phosphorus in rain, snow and atmospheric particle deposition is sufficient to support heavy algae growth. Utah Lake’s bottom sediments are also extremely rich in phosphorus.
- Given strong scientific evidence that even the largest possible reduction in inflowing phosphorus would not significantly reduce algae growth in Utah Lake, why would anyone want to spend many hundreds of millions of dollars, paid in our sewer bills, and additional huge costs to reduce other sources? To put it mildly, it does not seem rational.
- In a broader view, many of Utah’s headwater and upland lakes and reservoirs are nutrient-limited, and, in some, reducing inputs may decrease algae growth enough to make a significant difference in water quality. But even then, we need realistic evaluations of benefits to be gained as compared to costs, rather than mainly an “ideological hope” for better water quality. For Utah Lake, phosphorus-removal benefits would be very small and costs astronomical. Even compulsive gamblers would not put any more money into this one.
Utah Lake is a wonderful resource. It is tough and resilient. It is not seriously polluted. It harbors a rich and diverse ecosystem. Let’s embrace it as a fantastic basin-bottom lake that, admittedly, has some characteristics that some people don’t like. However, to try to change it into something that it cannot become will only result in frustration, even dismay, when it fails.
Much can be done to make shoreline and recreation areas nicer — better “housekeeping” would help tremendously, as would more and better access and recreational facilities. A well-funded nature center/lake research station would be a great asset. Let’s rally our resources and spend our dollars on these types of things rather than futilely trying to make Mother Nature change her laws.
LaVere B. Merritt is a professor emeritus of civil and environmental engineering. His research includes many multidisciplinary steam and lake studies, including Utah Lake. He is a consultant on Utah Lake issues. His white paper on Utah Lake addresses many of the lake’s physical and ecological characteristics.