8277 - Laserfiche WebLink

Home Browse Search

In the UCOL study unit, areas of intensive agri- culture are located in the Grand Valley and the Uncompahgre River Valley (fig. 2). Both areas have been used for agriculture since the 1880's. Extensive systems of canals and ditches provide the means for delivery of irrigation water, and many drains have been developed to carry the irrigation return flows to rivers and streams in the two areas. A synoptic study investigating the water quality of agricultural drains in the Grand and Uncompahgre River Valleys was conducted in May 1998. Water samples collected from a network of 43 river, stream, and drain sites were analyzed for physical properties and chemical constit- uents, nutrients, major ions, pesticides, and suspended sediment. This report focuses only on the pesticide data. May was chosen as the time period for the synoptic sampling because pesticides were frequently detected in this month in the fixed-station sampling during the previous year, and May is early in the growing season. Site selection for the synoptic study was based on the availability of historical pesticide- occurrence data (Butler and others, 1991, 1994) and on the spatial distribution of streams and drains. Twenty-three sites in the Grand Valley area (herein- after Grand Valley), including two sites in the fixed-station network pesticide-sampling scheme, were sampled once in May 1998 (fig. 2, table 3). Twenty sites in the Uncompahgre River Valley area (hereinafter Uncompahgre River Valley), including one fixed-station pesticide-sampling site, were sampled once in May 1998 (fig. 2, table 4). The Gunnison River near Grand Junction site (URV20), located downstream from the Uncompahgre River Valley, is included in table 4 with the Uncompahgre River Valley sites because its streamflow includes all of the streamflow of the Uncompahgre River Basin. Table 3. Agricultural synoptic surface-water-sampling sites, Grand Valley, Upper Colorado River Basin [USGS, U.S. Geological Survey] Site number (fig 2) Site name USGS site number Sampling date GVl Drain at 36 Road, East Orchard Mesa 390517108230501 05/05/98 GV2 Drain at C 1/2 and 33 3/4 Roads, Central Orchard Mesa 390322108253401 05/05/98 GV3 33 Road Drain at mouth near Clifton 390347108265800 05/05/98 GV4 Lewis Wash near Grand Junction 09106200 05/05/98 GVS Drain at D and 29 3/4 Roads 390345108073301 05/06/98 GV6 Drain at C 1/2 and 28 1/2 Roads 390319108312501 05/06/98 GV7 Indian Wash at C 1/2 Road 390320108315901 05/06/98 GV8 Orchard Mesa Drain at Grand Junction 09152600 05/07/98 GV9 Leach Creek at Durham 09152650 05/06/98 GV 10 Drain along Redlands Parkway, at mouth 390514108373201 05/07/98 GVl l Appleton Drain near mouth at G Road 390624108374900 05/07/98 GV 12 Limekiln Gulch near mouth 390529108385401 05/07/98 GV 13 Persigo Wash at River Road 390645108390101 05/11/98 GV14 Copeco Drain near mouth at Hwy 50 390723108400500 05/11/98 GV 15 Hunter Wash at River Road 390717108400501 05/12/98 GV 16 Goodwin Drain at Highway 50 390747108405600 05/12/98 GV 17 Adobe Creek near Fruita 09152900 05/12/98 GV 18 Little Salt Wash at Hwy 50 390938108443101 05/12/98 GV 19 Big Salt Wash at Fruita 09153270 05/13/98 GV20 Reed Wash near Loma 09153300 05/13/98 GV21 Reed Wash near Mack 09153290 05/08/98 GV22 Salt Creek near Mack 09163490 05/13/98 GV23 Colorado River near Colorado-Utah State Line 09163500 05/20/98 INTRODUCTION 7