Widespread western drought continues
By Summit Voice
As California experiences its worst drought in more than a century, it’s probably not surprising that some stream gages in the northern part of the state are showing all-time record low readings, with 2013 in the record books as the driest calendar year in the state’s 119-year recorded history.
Low streamflow affects water availability for agricultural, municipal, and industrial uses, water quality, water temperature, recreational opportunities, and the maintenance of fish populations.
Recent precipitation has resulted in some increases in streamflow, snowpack, and reservoir levels, but severe drought conditions remain. Without significant additional precipitation, prior conditions will quickly return leaving most streams in the state at less than 10 percent of normal for this time of year.
The U.S. Geological Survey is reporting that many of the nearly 500 stream gages in the state are currently at “below normal” or “much-below normal” flows for this time of year. Forty-one low-flow measurements have been made in the northern parts of the state, 12 of which have been measured at record low flows.
Water deliveries from the State Water Project and Bureau of Reclamation’s Central Valley Project to urban residents and farmers have been severely cut or even eliminated in some instances. As of February 12, 2014, the California Department of Water Resources measured the statewide water content of snowpack at only 27 pecent of the average for this time of year.
According to the USGS, the drought will also increase pressure on groundwater resources. In a press release, the federal agency pointed out that, once new wells are drilled during droughts, it is common for the resulting groundwater-use increases to remain in effect long after the droughts have passed.
California’s drought will also increase pressure on upstream resources, including the Colorado River, which only delivered 75 percent of average to Lake Powell during January. That leaves Lake Powell more than 120 feet from full pool, at 40 percent of capacity.
At the beginning of water year 2014, total system storage in the Colorado River Basin was 29.9 million acre feet (50 percent of capacity). This is about 4 million acre feet less than the total storage at the beginning of water year 2013 which began at 34.0 million acre feet (57 percent of capacity).
The picture could improve slightly this spring. Seasonal snowfall to-date in the Colorado River Basin is at 111 percent of the median, so the U.S. Bureau of Reclamation is forecasting near-average inflows for April to July, the key runoff season. Based on those projections, storage in Lake Powell will peak at about 50 percent of capacity this summer, the agency said, highlighting uncertainties linked with snowfall during the next few months.
2013 was the latest in a series of up and down years for Colorado River flows, but the bottom line is that, during the past 14 years, flows were above average only three times. The same span includes some of the driest years on record for the Colorado River Basin.
The 2000-2014 period is the lowest 14-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.25 maf, or 76 percent of the 30-year average (1981-2010) — that’s more than 2 million acre feet less than during the 1981-2010 total water year average.
The driest year during that span was 2011, when the river delivered just 2.64 million acre feet to Lake Powell.
Under the current forecast, total water year 2014 inflows to Lake Powell are expected to range between a minimum probable of 7.92 maf (73 percent of average) and a maximum probable of 13.47 maf (124 percent of average) with a most probable projection of 10.42 maf (96% of average).