Feb. 14, 2014 -- The state of California is experiencing its worst drought in over a century, and the lack of precipitation for much of the past three months has exacerbated the dryness, causing varying degrees of low levels of streamflow in the northern two-thirds of the state.
Low streamflow can affect water availability for agricultural, municipal and industrial uses, water quality, water temperature, recreational opportunities, and the maintenance of fish populations. Many of the nearly 500 stream gages are currently at below normal flows for this time of year. Likewise, 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 eliminated in some instances. As of February 12, the California Department of Water Resources measured the statewide water content of snowpack at only 27 percent of the average for this time of year. California snowpack melts into streams and reservoirs, providing about one-third of the water used by California's cities and farms.
During periods of drought, groundwater use can increase, but it is generally drawn in part from groundwater that may be slow to replenish. Also, once new wells are installed during droughts, it is common for the resulting groundwater-use increases to remain in effect long after the droughts have passed. About 20 percent of the nation's groundwater pumping occurs in the Central Valley of California, which contributes to 8 percent of the country's agricultural output and 25 percent of its food source.
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. Further, USGS crews from the California Water Science Center are monitoring conditions on a continuing basis.