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Published March 24, 2011
Streamflow Forecast(for spring and summer)
Data Source(s): National Water and Climate Center
The spring–summer streamflow forecast for the Southwest, issued on March 1, shows below-average flows for basins in the Mogollon Rim region of Arizona and New Mexico basins and near- to above-average flows for most of the Upper Colorado River Basin (Figure 12). Streamflow forecasts become more accurate as the winter progresses. However, spring storms can still have a large effect on actual spring streamflows.
In the Upper Colorade River Basin, winter precipitation has been above average. As a result, there is a 50 percent chance that inflow to Lake Powell will be about 116 percent of the 1971–2000 average for April–July, or 9 million acre-feet, which is a slight increase from the forecast issued on February 1. Dry conditions in most of Arizona are reflected in the streamflow forecast for the state; spring streamflow in the Little Colorado, Verde, Salt and Gila rivers are 18, 42, 22, and 23 percent of median, respectively.
In New Mexico forecasts for the Rio Grande Basin range from 30 percent of average for the Rio Pueblo de Taos below Los Cordovas to 82 percent of average for the El Vado Reservoir inflow. Flows for the Rio Grande at Otowi Bridge are forecast to be around 63 percent of average. For the Canadian River Basin, forecasts range from 40 percent of average for the Conchas Reservoir Inflow to 78 percent of average for Ponil Creek near Cimarron.
Since the water year began October 1, most of Arizona and New Mexico have received below-average rainfall, particularly in southern regions of both states where rain and snow have totaled less than 50 percent of average. The dry southern regions reflect the influence of La Niña events, which often deflect the storms north. In January, most of New Mexico and Arizona received scant precipitation; it was the driest January on record for New Mexico, according to the NOAA-Climate Prediction Center.Notes:
Water supply forecasts for the Southwest are coordinated between the National Water and Climate Center, 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 12 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 produces for Arizona between March and April, and for New Mexico between March 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 12. The CBRFC provides a range of 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
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
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