Hydrology of Area 61, Northern Great Plains and Rocky Mountain Coal Provinces, Colorado and New Mexico

Home Browse Search

3.0 WATER USE -- Continued 3.3 Use Classification of Streams Stream -Use Classifications Vary Between the Mountainous and Plains Regions Use classifications for mountain streams require better water quality than those forplains streams. Stream segments have been classified for various uses in Area 61 (fig. 3.3 -1). The mountain streams are classified for use as cold -water fisheries, for public water supplies, for primary- or secondary - contact recreation, and for agricultural use. Plains streams are classified for use as warm -water fisheries, for secondary- contact recreation, and for agricultur- al use. The classifications are intended to protect stream -water quality so that it is suitable for the indicated use. In Colorado, the classifications were made by the Colorado Department of Health (1980). In New Mexico, the classifications were made by the New Mexico Water Quality Control Commission (1977). The use classifications shown in figure 3.3 -1 have been generalized somewhat to account for differ- ences in language between use classifications between the two States. Associated with each use classifica- tion are numerical water - quality standards for specif- ic water - quality constituents. The numerical standards for certain water -qual- ity constituents may differ between the States for a given use classification. Because of different ambi- ent water quality, the numerical standards also may differ from one stream segment to another classified for the same use within Colorado. The divisions shown in figure 3.3 -1 between the upstream and downstream segments of some of the New Mexico streams are approximate. The divisions are based on 32 the location where the stream changes from perennial to intermittent. Many water - quality constituents may affect the suitability of water for a specific use. For fisheries, among the most important constituents are tempera- ture; dissolved oxygen; pH; many metals; some inorganic constituents, such as ammonia; and some pesticides which are toxic to fish. Water - quality constituents of concern in public water supplies are those which may have toxic effects, such as lead, selenium, or mercury; those which may cause gas- trointestinal problems, such as sulfate, or other adverse physiologic effects, such as fluoride; those which may cause problems of taste or odor, such as large concentrations of dissolved solids; those which may cause corrosion of pipes, such as acidity; and those which may cause stains on laundry or por- celain, such as iron or manganese. Of primary concern in waters used for recreational purposes, such as swimming or boating, are fecal - coliform bacteria, which are used as an indicator of the presence of organisms which may cause disease when ingested. Waters intended for agricultural use, espe- cially irrigation, commonly are judged for suitability on the basis of specific conductance or dissolved - solids concentration in conjunction with the concen- tration of some other constituents, such as boron, which may be toxic to certain plants.