Laserfiche WebLink
<br /> <br />however. Beaver Reservoir is located on the East Fork of Minnesota <br />Creek and has an absolute decreed capacity of 1,620 acre-feet and a <br />conditional decree of 522 acre-feet. Both reservoirs store water for <br />irrigation purposes and are filled during spring runoff. They are <br />usually drained by late August or early September. <br />Water quality data has been collected at several sites throughout the <br />Minnesota Creek drainage. The data indicate that these waters are of <br />calcium bicarbonate type with relatively low total dissolved solids <br />concentration. <br />Minnesota Reservoir appears to have an effect on the water quality <br />characteristics of Dry Fork. Detention of Dry Fork flows in the <br />Minnesota Reservoir results in a decrease in total suspended solids <br />(TSS) or turbidity, a slight increase in temperature, dissolved oxygen <br />(DO), and total dissolved solids (TDS). The increase in TDS is most <br />]ikely a result of evaporation losses. There is a slight increase in <br />alkalinity and, as a result, a slight increase in pH. In all <br />likelihood, these changes are also a result of evaporation losses. All <br />of the changes in water quality observed are what would be expected as a <br />result of impounding water in a shallow reservoir in a semi-arid climate. <br />There are over 100 springs located throughout the Mt. Gunnison <br />life-of-mine area. Measurements indicate that spring flows generally <br />decrease from a high in the early summer to a low in the fall. A number <br />of the springs are ephemeral, indicating that their sources are small <br />localized aquifers.(i.e. landslide deposits, colluvium, lenticular <br />sandstones, etc.). <br />5. Precipitation and Runoff <br />Only two precipitation stations exist for the watershed, one at Paonia <br />and one at the Mt. Gunnison mine. Since these are located near the <br />North Fork of the Gunnison River, they may not be representative of the <br />total watershed. Isohyetal lines can be used to show average <br />precipitation that falls on the watershed. Figure 4 represents mean <br />annual precipitation and Figure 5 illustrates May to September <br />precipitation of the years 1931 to 1960. All values were obtained from <br />maps drawn by the U.S. Weather Bureau. Table 7 summarizes precipitation <br />data for both the north and south sections of the watershed. Comparing <br />these isohyetal maps with Figure 6 shows that precipitation patterns are <br />strongly influenced by topography. <br />During the period May through September, the amount of precipitation <br />which falls upon the watershed is less than the potential amount of <br />water lost to evapotranspiration (PET). In other words, transpiration <br />by native vegetation and evaporation consumes most of the precipitation <br />and also will remove water from the soil profile. For those areas where <br />cash crops such as apples, peaches, and the like are grown, irrigation <br />water is removed from the North Fork of the Gunnison River and applied <br />on such lands. <br />41 <br />