Note: This publication is currently undergoing major revisions. The current publication will be replaced with a new publication based on stakeholder requirements and scientific advances. We expect to begin sharing details on this soon. If you have input on content, format, or publication frequency at any time, please contact us at cbrfc.webmasters@noaa.gov.Lower Colorado Water Supply Outlook, March 1, 2011

Lower Colorado Water Supply Outlook, March 1, 2011


Prepared by G. Smith
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Lower Colorado Summary






*Median of forecasts within each basin.


Salt Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation was near 80 percent of average in the upper Salt River Basin and 90 to 130 percent of average in the Verde River Basin.

February precipitation was 75 percent of average in the upper Salt Basin and near average in the Verde Basin.

Streamflow:
February streamflow was near 30 percent of median on the Salt River, 45 percent of median on the Tonto, and 75% of median on the Verde River.

Snow:
March 1st snowpack varied from 50 to 165 percent of average in the Verde River Basin, with the majority of sites reporting below average conditions. Snowpack in the upper Salt River Basin was generally less than 65 percent of average. In all areas snowpack was limited in areal coverage.

Salt River Basin Snow Plot.
Verde River Basin Snow Plot.

Soil Moisture:
Below average precipitation during the late summer and fall resulted in below average modeled soil moisture states in the upper Salt River Basin. Wetter soil moisture conditions exist in the Verde Basin as more frequent precipitation events have occurred this winter.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
February storms affected primarily the upper Verde and western Arizona with near to above average precipitation for the month. The Salt River Basin experienced below average precipitation and entered the runoff season with drier soil moisture conditions compared to the Verde Basin. While a few sites reported above average snowpack conditions, most areas have recorded much below average snowpack. Streamflow in February was also well below median.

These conditions are somewhat consistent with La Nina climate conditions that currently exist. Below average precipitation and below median runoff are observed more frequently during La Nina events. March-May forecast volumes are for 20 percent of median in the Salt River Basin, near 35 percent of median in the Tonto Basin, and near 40 percent of median in the Verde Basin.



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Gila Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation was ranged from near 30 to 50 percent of average.

February precipitation was ranged from near 30 to 45 percent of average.

Streamflow:
February streamflow was near 35 percent of median.

Snow:
March 1st snowpack conditions were near 50 percent of average in San Francisco Basin and 20 to 40 percent of average in the upper Gila Basin.

Upper Gila Basin Snow Plot.
San Francisco Basin Snow Plot

Soil Moisture:
Below average precipitation has resulted in below average modeled soil moisture states.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
Several conditions exist that support much below median March-May streamflow volumes in the Gila River Basin. These include below average seasonal precipitation and soil moisture, and much below average snowpack. The presence of La Nina climate conditions suggest drier than average conditions have a better chance of occuring through the forecast period. March-May forecast volumes range from 15 to 30 percent of median.



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Little Colorado Basin Conditions

The following conditions influenced this month's forecasts:

Precipitation:
Seasonal October-February precipitation ranged from near 60 percent of average in the headwater locations up to 125 percent of average near the basin outlet.

February precipitation ranged from 65 to 105 percent of average throughout most of the Little Colorado Basin.

Streamflow:
February streamflow on the Little Colorado at Lyman was near 45 percent of median.

Snow:
Basin snowpack conditions on February 1st were near 70 percent of average in the southern Headwaters.

Little Colorado Southern Headwaters Snow Plot
Central Mogollon Rim Snow Plot

Soil Moisture: Modeled soil moisture states varied throughout the Little Colorado. Below average seasonal precipitation resulted in below average soil moisture conditions in the headwater locations. Elsewhere soil moisture conditions were similar or wetter than last year entering the runoff period.

Climate Forecasts:
La Nina climate conditions suggest decreased chances for precipitation in this area. The La Nina influence was accounted for in generation of these forecasts.

Forecast Summary:
The presence of La Nina climate conditions suggest below average precipitation into the spring. Below average seasonal precipitation exists over most of the Little Colorado Basin, with below average soil moisture conditions in the headwaters. Snowpack conditions changed little from February 1st to March 1st, and remain below average. March-May streamflow volumes are forecast to range from near 15 to 40 percent of median.



* Percent usable capacity, not percent average contents.
Click for multi-month Graph.







Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).


Monthly Streamflows













Precipitation Maps








Hydrologist: G. Smith