- About Us
- SW Climate
Published May 22, 2013
Streamflow Forecast(for spring and summer)
Data Source(s): National Water and Climate Center
Rain and snow this winter were well below average in many parts of New Mexico and southern Arizona. Consequently, the spring–summer streamflow forecast for New Mexico, issued on May 1 by the Natural Resources Conservation Service (NRCS), calls for below-average flows in all river basins (Figure 13). No streamflow forecasts are issued in May for Arizona; the last forecast is published in April.
The best estimate for total March–July streamflow calls for a 50 percent chance that flows in the Rio Grande, measured at Otowi Bridge north of Albuquerque, will measure less than 24 percent of average for the April–July period. This is a decrease from the estimate made one month ago. Now that most of the runoff season has passed, even optimistic estimates suggest streamflow on the Rio Grande will be less than 33 percent of average. Steamflow on the Pecos River is also projected to be very low, with best estimates calling for flows to be less than 30 percent of average.
For the Colorado River, unregulated inflow volume to Lake Powell in April was 34 percent of average. The forecast for the lake for the April–July period also projects below-average flow. The likely range is expected to be between 24 and 59 percent of average, with the most probable estimate calling for a total of 3.0 million acre-feet (maf), which is 42 percent of the 1981–2010 average. Due to late season snow storms in the Upper Colorado River Basin, the forecast increased by 0.3 maf from last month. Based on the current forecast, Lake Powell elevation likely will decline by approximately 10 feet during the spring and summer. The elevation at the end of the water year likely will be 3,588 feet, with storage around 10.6 maf, or 44 percent capacity.Notes:
Water supply forecasts for the Southwest are coordinated between the National Water and Climate Center (NWCC), part of the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS), and the Colorado Basin River Forecast Center (CBRFC), part of NOAA. The forecast information provided in Figure 13 is updated monthly by the NWCC. Unless otherwise specified, all streamflow forecasts are for streamflow volumes that would occur naturally without any upstream influences such as reservoirs and diversions. The coordinated forecasts by NRCS and NOAA are only produced for Arizona and New Mexico between January and May.
The NRCS provides a range of forecasts expressed in terms of percent of average streamflow for various exceedance levels. The forecast presented here is for the 50-percent exceedance level, and is referred to as the most probable streamflow. This means there is at least a 50 percent chance that streamflow will occur at the percent of average shown in Figure 13. The CBRFC provides streamflow forecasts in the Colorado Basin ranging from short-fused flood forecasts to longer-range water supply forecasts. The water supply forecasts are coordinated monthly with NWCC.
For state river basin streamflow probability charts, visit:
For information on interpreting streamflow forecasts, visit:
For western U.S. water supply outlooks, visit:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubois, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer