9342 - Laserfiche WebLink

Home Browse Search

Water resources are in high demand year-round to support seasonal recreational activities. Photographs by Ken Neubecker. Low flows in Gore Creek are sustained primarily by ground-water discharge and the gradual melting of perennial snowfields. Knowledge about the expected frequency of certain low flows is important because of potential detrimental effects to stream biota resulting from depletion of dissolved oxygen and higher concentrations of dissolved contaminants in low flows. The 2-year and 10-year 7-day low flows (table 4) indicate the lowest mean streamflow for a period of 7 consecutive days that have a 50-percent or lO-percent chance, respectively, of not being exceeded in any given year the values range from no flow to 16 ft3/s (table 4). Water Quality Water-quality property and constituent data available for surface-water sites consist of field properties (specific conductance, dissolved oxygen, pH, and water temperature), inorganic constituents (major ions, trace elements, and nutrients), sediment (suspended sediment and bedload), and organic constituents (DOC, sac, pesticides, and VOCs). Data were collected at 37 sites throughout the Gore Creek watershed (fig. 5). Field Properties Field properties such as specific conductance, dissolved oxygen, pH, and water temperature are indi- cators of water-quality conditions. Specific conduc- tance provides a good measure of the amount of dissolved constituents in water. Adequate concentra- tions of dissolved oxygen are critical to aquatic life. Even infrequent periods of dissolved-oxygen depletion can have adverse effects on stream biota such as fish and macroinvertebrates. pH is a controlling factor for partitioning of trace elements in sediment and water. Low pH tends to increase solubility of trace elements in water. Streams with very low pH, such as found in streams affected by mining, can have much reduced or even nonexistent macroinvertebrate and fish communi- ties. Temperature influences metabolic rates in stream organisms. Aquatic organisms are adapted to specific temperature regimes; for example, trout are considered a cold-water fish. Specific conductance. Specific conductance is proportional to the dissolved-solids concentration in a given water sample. The major ions that compose dissolved solids for water samples from the Gore Creek watershed are calcium, magnesium, sodium, potassium, silica, chloride, sulfate, and bicarbonate. SURFACE WATER 25