Guest opinion: Why stream-flow gauging?
September 12, 2012
The onset of fall weather and colors feels like a welcome respite from one of the driest summers on record. Despite the monsoon rains that started in July, severe drought conditions persist throughout the entire state, with 64 percent of Colorado still experiencing extreme drought. By comparison, at this time last year only 9 percent of the state was experiencing extreme drought, according to the National Integrated Drought Information System (www.drought.gov).
One way to assess drought conditions is by monitoring streamflow, temperature and other indicators of stream health, measured electronically by streamflow gauges. These gauges provide vital information for water resource management locally, regionally and nationally. There are 35 stream-flow gauges currently operating in the Roaring Fork watershed, six in the Fryingpan basin alone as a result of the Fry-Ark diversion project, including Reudi Reservoir. Another 50 streamflow gauges that functioned in the watershed at earlier periods of time no longer operate.
Most stream gauges operate by measuring water depth (called “stage”) and converting that to streamflow (“discharge”) by using a curve created from manually collected data that relates depth to a set of discharge measurements specific to that site. These data are recorded and transmitted via satellite for real-time viewing.
It is possible to co-locate additional data sensors with the gauges to measure water-quality parameters such as temperature, conductivity, pH, dissolved oxygen and turbidity. This creates a data set that paints a far better picture of what is happening in the river. For example, co-locating flow and temperature gauges would allow assessment of the relationship between high and low streamflows and their associated temperature. Currently, only two gauges in our watershed – the Roaring Fork at Glenwood Springs and Castle Creek at Aspen – measure stream temperature.
Stream-gauge data provide information to support a wide range of uses such as flood control and warnings, drinking-water management, wastewater discharges and reservoir releases and measuring, administering and enhancing instream flows. In most uses, long-term data records are most valuable because they allow water managers to discern changes in streamflow as a result of water and land use or climate change. The longest continuously operating gauge in the watershed, on the Roaring Fork River at Glenwood Springs, has been in operation since 1906.
The Crystal River provides a good example of why a long-term data record is important. The U.S. Geological Survey gauge on the Crystal River below Carbondale operated only from 2000 to 2010 (a short period of record). To better administer water rights during low flow conditions in 2007 the Colorado Department of Water Resources installed another gauge upstream of the old, unoperated Geological Survey gauge at the fish hatchery. This gauge only operates seasonally and has an even shorter record. In this record-setting drought year, it was impossible to accurately compare current streamflows in the lower Crystal River to other drought years such as 2002 and 1977.
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The Roaring Fork Watershed boasts more gauges than many other watersheds in the state partly because people here care about the rivers and partly because of the extensive transbasin diversions from the Roaring Fork, the Fryingpan and Hunter Creek to the Front Range. At least 25 of the 35 operating gauges are related to transmountain diversions.
In an era of climate change and intense competition for water supplies, water managers, elected officials and the public in the Roaring Fork watershed will have to identify and answer questions that go beyond water administration – questions concerning ecosystem health and resiliency in the face of increasing pressures from land-use change and climate change. Indeed, these are important questions faced by many communities across the western U.S.
Gauges are most useful if they can be located to tell us about vulnerable reaches in the river. For example, the gauge for the upper Roaring Fork near Aspen is above Salvation Ditch. Over the past month, flows recorded at that gauge have been consistently higher than what is flowing through Aspen because a substantial amount of water is diverted out of the river, just below the gauge.
Friends of Rivers and Renewables, the Roaring Fork Conservancy and other partners have developed a plan for a system of “smart gauges” that can be strategically located in our rivers and streams to collect data we will need to address these questions. The proposed network of gauges is designed to collect data that can help water managers tackle the difficult job of meeting human needs while maintaining sufficient flows to promote stream function and integrity. Given our shared appreciation for rivers and streams, and the tradition of environmental leadership in local governments in the Roaring Fork watershed, the gauge network could be a vital proving ground for a 21st-century water-management paradigm that moves beyond the past century’s pitched conflicts of human need versus stream health and instead chooses both, or “all of the above.”
Learn more about this new gauging initiative on Friends of Rivers and Renewables’ and the Roaring Fork Conservancy’s websites (www.forraspen.us and http://www.roaringfork.org).
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