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The ditch is "turned on" usually in mid-April, and continues to operate up until about mid-October, <br />depending on the length of each year's growing season. During the remainder of each year, the ditch is <br />temporarily turned on to provide water for filling cisterns and stock ponds. Water delivered via this lateral <br />and the rest of the surrounding ditch system provides a water source for irrigation, drinking water and <br />livestock use, and is the dominate seasonal influence of the hydrologic regime in the vicinity of the New <br />Horizon Mine. <br />As a part of baseline studies initiated in and near the New Horizon 2 mining area, three surface water <br />monitoring sites were established along the West Lateral for obtaining flow and water quality baseline <br />information. These sites were SW -N104, SW -N105 and SW -N106 and were located on the West Lateral at <br />points upstream, midway and downstream of the New Horizon 2 mining area (see Map 2.04.7-1A). Flow <br />and water quality data were collected at these sites since July of 1986, and are presented as Stream Gaging <br />Report and Water Quality Reports presented in Peabody Appendices 7-5 and 7-9, respectively. Monitoring <br />of the site SW -N106 has been discontinued. However, New Horizon Mine continues to monitor SW -N104 <br />and SW -N105. <br />Surface water Site SW -N104 is located on the West Lateral, in the city limits of Nucla. Instantaneous <br />discharge measurements were made at SW -N104 in the diversion splitte box, and continuous flow <br />monitoring were conducted at this site via a stilling well and a digital water level recorder located in the <br />channel upstream of the splitte box. Coupled with the continuous stage record, measurement of <br />instantaneous discharge overtime will yield a stage versus discharge rating curve for SW -N104. Discharge <br />measurements indicated that irrigation flow varied from a high of 27.6 cfs (August, 1986) to a low of 14.9 cfs <br />(August, 1987). Flow occasionally receded to a trickle during the irrigation season, when water in the ditch <br />was temporarily turned off due to routine maintenance or unforeseen problems up -stream in the main ditch. <br />Surface water Site SW -N105 is located on the West Lateral at about the midway point between Sites <br />SW -N104 and SW -N106. Instantaneous discharge measurements were conducted at this site in a wooden <br />splitte box. Measured flow values are summarized for each month and are included with stream gaging <br />flow reports presented in Attachment 2.04.7-8 (Peabody Appendix 7-5). Measured discharge ranged from <br />9.2 cfs (August, 1987) up to 14.7 cfs (May, 1987). <br />Surface water Site SW -N106 was the most -downstream monitoring site located on the West Lateral <br />irrigation ditch. As at SW -N104, instantaneous discharge measurements were made at SW -N106 in the <br />diversion splitte box, and continuous flow monitoring was conducted at this site with a stilling well and <br />recorder also located in the channel upstream of the splitte box. A stage -discharge curve will be more <br />defined over time at this site, as more measurements of instantaneous discharge are obtained and correlated <br />with the continuously recorded stage measurements. Measurements of instantaneous discharge indicated <br />that the ditch delivers irrigation water to the location of SW -N 106 for a range of from 7.0 cfs (August, 1987) <br />up to 12.4 cfs (May, 1987). Measured instantaneous discharge values can be found in Peabody Attachment <br />2.04.7-8 (Peabody Appendix 7-5). The ditch flow recedes almost to zero during periods of ditch <br />maintenance. <br />A "gain -loss" study was performed on the West Lateral irrigation ditch on July 7 of 1986. Measurements of <br />instantaneous discharge were collected along the ditch course at select diversion locations just upstream of <br />each diversion of irrigation water. Measurements were made using a Marsh-McBirney flow meter for <br />obtaining velocity readings, and a tape measure for determining the cross sectional area of the channel at <br />each measurement location. <br />Sixty two percent of the ditch water was either diverted or lost (due to evapotranspiration and seepage) from <br />Page 2.04.7-23 March 2017 (TR -77) <br />