HangmanTMDLConcerns

Hangman (Latah) Creek
Water Quality Improvement/Total Maximum Daily Load (TMDL) Project

Water Quality Concerns

Hangman (Latah) Creek has been identified by the Department of Ecology as not achieving state water quality standards for several factors covered by Section 303(d) of the Clean Water Act, including fecal coliform, dissolved oxygen, turbidity, ammonia, pH and temperature. Recent monitoring has identified several other water quality problems not specifically addressed under Section 303(d) of the Clean Water Act, including sediment load, low flows and total phosphorus.

The lack of vegetative cover along the streambank can result in increased water temperatures which affect fish and other aquatic species.

Temperature : Temperature is significant for the health of aquatic life. Fish, particularly salmonids (trout and salmon, and other aquatic life need cooler temperatures to survive and spawn. Water temperature also directly affects the solubility of oxygen in water, the metabolic activity rate of bacteria, and the geochemical reaction rates. The warmer the water, the great the ill effects and the less dissolved oxygen for fish to breathe and for chemical reactions. For cold water biota and trout, the duration of temperature exceedences is as important as the temperature and the number of temperature exceedences. Hangman Creek has continuously violated this water quality parameter for decades. The majority of sampling by the Washington State Department of Ecology and the Conservation District indicate a serious problem throughout the basin. The lack of riparian vegetation along the stream is generally considered the main source for the problem.

Learn more about temperature through the Department of Ecology's focus sheet: Effects of Elevated Water Temperatures on Salmonids

pH: The pH indicates the acidic or basic quality of the water. The pH level affects the chemistry and chemical reactions in the water, impacting the fish, other aquatic wildlife and plants. The Department of Ecology has monitored pH for many years on Hangman Creek. Historic pH values have ranged from ranged from 6.34 to 9.41. The high pH values generally occurred during low flows and have been attributed to excessive algal respiration that increases with nutrients supplied from human activity.

The Department of Ecology has created a pH Value Scale that indicates the various effects pH has on aquatic life.

Livestock waste is a common source
of fecal coliform.

Fecal Coliform: Fecal coliform bacteria is significant for human health as an indicator of the presence of disease-carrying organisms. It commonly comes from livestock and failing septic tanks. Ecology has found fecal coliform problems in the past and the SCCD has conducted extensive sampling that should all sites met the Class A criteria for fecal coliform. Recent sampling for this project, however, has found exceedences for 13 out of 17 sample sites. Exceedences were found on Hangman Creek, Rock Creek, Spangle Creek, Cove Creek and California Creek. Only Marshall Creek was found to be within the water quality standards.

Learn more about fecal coliform through the Department of Ecology's focus sheet: Fecal Coliform Bacteria and Washington's Water Quality Standards

Dissolved Oxygen: Dissolved oxygen (DO) is important in stream systems because the higher forms of aquatic life require oxygen for survival. In addition, oxygen is important for the decomposition of organic matter and for other biological processes. The Conservation District’s monitoring program (1994-1997) documented 29 exceedences (out of 172 samples). Recent sampling for this project has found exceedences on Hangman Creek, Rock Creek and Marshall Creek.

Learn more about dissolved oxygen through the Department of Ecology's focus sheet: Dissolved Oxygen and the Water Quality Standards

Ammonia: Ammonia is an indication of nitrogen, a nutrient that affects plant and algae growth. Too much ammonia/nitrogen can result in excessive plant growth, leading to changes in the water's chemistry, oxygen levels and clarity.

Learn more about the affects of ammonia through the Department of Ecology's focus sheet: Nutrients in Our Lakes and Streams

Turbidity: Turbidity refers to the amount of suspended solids in the water. These solids may include soil particles, algae, and other materials. Excessive amounts of material mean that light cannot penetrate the water, impacting the photosynthesis of plants and thus the amount of oxygen being produced.

Erosion of streambanks results in sediment in Hangman Creek and other waters in the Hangman watershed. The erosion is the result of many factors, including road construction, livestock grazing and the removal of stabilizing vegetation.

Sediment (Suspended and bedload): Suspended and bedload sediment have been a severe problem in the basin. The SCCD conducted a study to quantify the annual bedload and suspended sediment discharged to the Spokane River. The total sediment discharged (annual bedload and suspended load) from the mouth of Hangman was estimated for water years 1998-2001; 1998 (40,300 tons); 1999 (189,000 tons); 2000 (95,300 tons); 2001 (4,740 tons). The suspended sediment discharge contributed the majority of the total sediment load (87 and 72 percent for water years 2000 and 2001). Currently, there are no numeric criteria for sediment.

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