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0012. At all pool elevations, the reservoir is dendritic and the shoreline is very irregular. At minimum pool (30,355 acre-ft), the reservoir is about 3.5 mi long and varies in width from a few hundred feet to about 1.3 mi. Between 1985 and 1987; the reservoir had a l~ngth of more than 9 mi, a width that variea from leas than 0.3 to about 2.2 mi, a depth that varies from a few feet near the inflow to about 155 ft at the dam, and a shoreline of about 60 mi. . SAMPLING-SITE LOCATIONS AND TYPES AND METHODS OF DATA COLLECTION AND ANALYSES After an initial reconnaissance of Pueblo Reservoir in May 1985, seven transects were_established from the inflow (pl. 1, transect 1) to the dam (pI. 1, transect 7). Three monitoring sites 'were selected along each transect. During 1986, an additional 5 trib~tary sites were included as part of the monitoring network. Water-quality data collected from Pueblo Reservoir consist of onsite measurements and laboratory analyses of chemical and biological constituents. Reservoir sites were selected for various monitoring purposes. Therefore, not all measurements and analyses were done at every site. Onsite measurements of light transparency, water temperature, pH, dissolved oxygen, and specific conductance were made at 26 reservoir sites. Light transparency was measured with a Secchi disk, which is a white, flat, circular disk about 8 in. in diameter. The measurement consists of recording the depth at which the disk disappears from view. Measurements of water temperature, pH, dissolved oxygen, and specific conductance were made in-situ by using a multiparameter meter. The meter was calibrated each morning before beginning onsite measurements. During 1985, these in-situ measurements generally were made at 3-ft depth intervals from the reservoir surface to the reservoir bottom at all the sites within each transect to evaluate cross-sectional mixing in the reservoir. During 1986-87, the in-situ profile measurements were made mo:re frequently than during 1985, but were made routinely at 3-ft depth interva'ls from the reservoir surface to the reservoir bottom only at sites IB, 2B, 3B, 4B, 5C, 6C, and 7B. During 1986-87, in-situ profile measurements were made at 5 discrete depths at the other 19 reservoir sites. Diel profile measurements of water temperature, pH, dissolved oxygen, and specific conductance were made at selected reservoir sites once in 1986 and twice in 1987 to monitor variations that occur over a 24-hour period. In addition to onsite measurements, water samples were collected at the middle site of each transect (sites IB, 2B, 3:8, 4B, 5C, 6C, and 7B) for chemical analyses. Samples were collected from near the reservoir surface and from near the reservoir bottom using a 4-L, non-metallic, 2-ft-long water- sampling bottle. Additional samples were collected periodically for analyses of selected constituents from a third depth at selected sites when the reservoir was. not completely mixed. During 1985, samples were collected at additional sites within the transects that were located immediately downstream from tributaries (transects 3, 5, 6, and 7) for nitrogen and phosphorus analyses. During 1986-87, additional water samples were collected from 3 to 5 discrete depths at 26 reservoir sites for turbidimetric analyses to evaluate transport of particulate material in the reservoir. 4