Upper Los Pinos Water Quality Report

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Water-Quality Data Synthesis for the Upper Los Pinos River Watershed, Southwestern Colorado, and Suggestions for a Watershed Plan, 2005 By Winfield G. Wright Certified Professional Hydrologist Abstract The upper Los Pinos Rig°er ~ti°atershed contains high- altitudelakes, mountain streams and rivers. and Vallecito Reservoir (pronounced T psi. y~~. sito), which is a man-made reservoir completed in 1942 for irrigation of agriculhiral lands in the lower Los Pinos River watershed. The watershed generally has good ~~- ater qualitc :however, there is potential for stresses on the hydrologic and ~~-~ater-quality- sy stem. such as wildfires. housing developments. recreation, and atmospheric deposition from po~yer plants. Historical water-quality data from the upper Los Pinos River watershed indicate that selected water-quality constituents show an improving trend over time. Constihents in high-altihide lakes show improving trends in chloride. iron. and pH. Constituents in Vallecito Creek upstream from Vallecito Reservoir sho«-• improving trends in chloride, ammonia, gross beta (Cesium-137) radioactivity, and pH. The improving trends are statisticall~~ significant however, the causes for the improving trends are unknown. Water-qualitc~ data from Los Pinos River below Vallecito Reservoir shows the effects of the Missionai~~ Ridge ~yildfire. Specific conductance values, pH. and nitrite+nitrate concentrations have increased in water do~ynsheam from the dam. Water-quality- data from Vallecito Reservoir show some impacts from the Missionary Ridge wildfire of 200?. Specific conductance values have increased since the wildfire, and dissoh ed-oly gen concentrations were as low as 0.3 mg/L, resulting in a fish kill of kokanee salmon in the lake during August 2003. Dissolved-olygen concentrations also were as to«~ as 0.3 mg/L during September 2000, vet no fish were killed during that event There may be other factors involved ~yith the fish kill of 2003, such as increased iron and manganese concentrations due to sediment nmoff from the wildfire and anaerobic conditions created by nmoff of organic matter. Water-quality- samples for anal~~sis of dissolved metals have not been collected in Vallecito Reservoir since 2000: therefore, it is difficult to conclude the impacts of the ~yildfire on the lake ecosystem. Comparison of historical water-quality data to Colorado water-quality standards indicates that most of the waters in the upper Los Pinos River watershed meet the standards. A few constituents «,°ere sho~yn to elceed the standards in a fey locations--such as ammonia, total iron. pH, total phosphon~s, selenium, zinc, and fecal coliform in streams and ground water in the Vallecito Reservoir area. Dissolved-o~-~ gen concentrations in the resei-~-oir were below the standard of 6.0 mg/L. The goal is of this report to indicate where ~yater quality is good in the ~yatershed, and develop measures to make sure that the water remains of good qualitti. Suggestions for development of a watershed plan are provided. Development of a watershed plan requires input from the community, agencies, and tribes. Suggestions also are made in this report for continued water-quality monitoring. INTRODUCTION The upper Los Pinos River watershed eiemplifies a classic mountainous setting of high- altittide streams, mountain lakes, and alpine views. The watershed includes t<vo main streams--Vallecito Creek and Los Pinos River, which converge at Vallecito Reservoir, aman-made reservoir constructed in 1942 for storage and distribution of irrigation water to farmlands in the to«-er Los Pinos River ~~-atershed (fig. 1). Water quality of the streams and lakes in the upper Los Pinos River watershed is generally good: none of the water bodies in Los Pinos River watershed are listed as an impaired water body. Ho~~~ever, there are stresses on the watershed from «~ildfires, recreational use (boating, fishing, hiking, hunting, and horse packing), housing developments, and aUnospheric deposition from coal-fired po~~ er plants. The water quality- of the upper «atershed is related to the ~~~ater quality in the lo~~-er «-atershed where agriculture, energy development, and population growth have the potential to severehr stress the water- ,~' ~~ Southwest Hydro-Logic 1 W