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Major Storage Projects Reservoi r Normal Storage (acre-feet) 103,114 59,571 52,192 43,826 22,679 17,374 15,182 14,052 5,808 4,758 3,468 3,041 2,436 1,500 Sanchez Reservoir Platoro Reservoir Rio Grande Reservoir Santa Maria Reservoir Continental Reservoir Mountain Home Reservoir Terrace Reservoir La Jara Reservoir Smith Reservoir Beaver Park Reservoir Eastdale Reservoir No. 1 Eastdale Reservoir No. 2 Big Meadows Reservoir Head Lake Hydrological Variations Gage extremes for the Rio Grande near Del N orte, as the river enters the San Luis Valley, and at Lobatos, downstream of the last diversion in Colorado before the river enters New Mexico, are shown in the following table. Seasonal variations are shown below in the annual discharge graph. Gage Maximum Recorded Flow (cfs) 14,000 (1911) 13,100 (1905) Minimum Recorded Flow (cfs) 69 (1902) o (1950) Near Del Norte Near Lobatos Source: Colorado Department of Natural Resources Annual Discharges Rio Grande Near Del Norte WY 1912 -1998 5000 Average Annual Discharge: 4500 Minimum Annual Discharge: Maximum Annual Discharge: 657,400 AF 224,760 AF (1977) 1,071,041 AF (1987) D Avg Year . Max Year D Min Year 4000 "'C c: 8 3500 a> ~ 3000 a> a. a> 2500 a> ~ 2000 :c ~ 1500 1000 500 o Oct t-bv Dee Jan Feb Mar Apr May Jun Jul Aug Sep Source: US Geological Survey Water Data Reporls Major Water Rights Calls Usually by mid-July native flows in all of the basin streams have receded to the point that only the most senior water rights have water available to them and reservoir releases provide supplemental water. All streams in the Rio Grande Basin are on call throughout any normal irrigation season. The Rio Grande and the Conejos River system are on call year-round from water right calls and/or the Rio Grande Compact. Much of the Rio Grande mainstem surface water is used conjunctively with the groundwater system in order to provide a reliable irrigation season supply. The State Engineer has had a moratorium on new appro- priations from non-exempt confined aquifer wells since 1972 and on non-exempt unconfined aquifer wells since 1982. Agreements have been reached with all major water user groups, including both surface and groundwater interests, that have precluded the need for groundwater administration rules at the present time. The CWCB and the State Engineer's Office (SEO) are currently working on the Rio Grande Decision Support System (RGDSS) that will answer many outstanding basin concerns. Under the legislation that enabled the RGDSS, the SEO will promul- gate rules that address the potential for new appropriations in the confined aquifer. Stream and Lake Protection There are 133 instream flow segments totaling approximately 971 stream miles in the basin. There are also 48 lakes with decreed natural lake levels. These water rights are held by the CWCB to "protect the natural environment to a reason- able degree." The decreed flow or lake level for each of these instream flow segments and natural lakes is based on the amount required to maintain the water-dependent natural environment. Ephemeral stream in the Great Sand Dunes National Park (Photo courlesy of Adam Bingham) ( Rio Grande Basin Facts - 2 )