1. A greater array of possible release rates were prescribed for the spring runoff period. 2. The releases to meet the required January 1 flood control space were spread over five months rather than three. 3. The summer-fall storage space building releases were limited to a maximum rate of 28,000 cubic feet per second, rather than the earlier maximum of 40,000 cubic feet per second. These changes tend to reduce the incidence of damaging high flood flows and increase power production. Runoff Forecasts by the The Bureau's 1982-1983 water year operations have been criticized on the grounds that the Bureau "knew" that the winter snowfall was significantly higher than normal but ignored this information. This criticism may have been based on reports of high snowfall at a few locations in the Upper Basin states. There may have been extra high snowfall at some locations, but what is frequently overlooked is the vast extent of the Upper Colorado River Basin watershed as compared to other watersheds such as the Sierra Nevada in California, and how weather conditions are usually not uniform over the entire Basin. During the 1982-1983 season, although some areas were above normal during the entire year, other areas were below normal which resulted in February 1 and March forecasts of average April-July runoff. It was only the late-season precipitation that boosted the seasonlong precipitation of all of the Basin's immense areas to above-average levels. Study and analysis of this year's weather events may allow the National Weather Service Colorado River Forecast Center to improve future forecasts. Consideration needs to be given to including as parameters in making runoff forecasts, factors such as temperature that bear directly upon the efficiency of the conversion of the snowpack to stream runoff. The Weather Service uses the term "high efficiency" to describe when a high percentage of the snow is converted into runoff, which is what happened this year. One factor that caused a high efficiency this year was the effect of low temperatures in the Basin in April and May followed by high temperatures in June. In the past, the April 1 and May 1 forecasts have been fairly accurate, and operation plans have been made with a fair degree of certainty based on those forecasts. By considering other factors, it may be possible to obtain an earlier indication of unusual runoff events such as occurred this year, thereby increasing the reliability of the forecasts. Developments Within the Flood Plain For many years following the closure of Hoover Dam, the desired maximum flood control release of 40,000 cubic feet per second would have caused only minimal damage in the downstream floodway. As recognized in the Corps 1982 report and as this year's experience has demonstrated, a release of 40,000 cubic feet per second now causes significant property damages due in part to encroachments into the floodway. The businessmen and residents along the river, riverside communities, and the levels of government directly concerned should join in seeking a solution to the problems resulting from these encroachments into the floodway. Colorado River Water Resources In discussing the flood control operations at Hoover Dam and the other Colorado River reservoirs, it is well to remember that they were authorized by Congress as multipurpose reservoirs, and that the maximization of one purpose usually diminishes the benefits of the other purposes. As one of the major purposes of the Colorado River reservoirs is conserving water for irrigation, municipal and domestic uses, I would like to comment on the importance of the river's water supplies to the seven Colorado River Basin states. The river is the source for all of the present and potential water needs of the people residing on the lands within its drainage basin, and is the source for the supplemental water needs of urban and agricultural areas in the basin states that are located outside of the drainage basin. The river provides a full or partial water supply for about 15 million people and 3.9 million acres of irrigation. In 1985, the Central Arizona Project is scheduled to commence operations. Several years thereafter, water deliveries to Arizona coupled with increased water use in the Upper Basin states will push the annual water requirements on the river up to the level of the long-term dependable yield of the river. Thereafter, annual requirements in excess of the long-term yield will have to be met by continued drawdown of water in storage. Requiring release of water in excess of beneficial use increases the probability of reduced future use because the water that would have otherwise been in storage will not be there. This fact must be considered in reviewing flood control criteria. The history of the Colorado River is one of periods of mostly dry years interspersed with periods of mostly wet years. No one is able to predict when wet or dry periods begin or end. They are determined after the fact. In the past 53 years, there was one 10-year period and one separate 15-year period when the average annual flow was around 12 million acre-feet per year (maf/yr) which is about equal to the total current water use of river water. The University of Arizona has made a careful examination of tree rings in the Colorado River Basin and used them to estimate the basin runoff over the past 450 years. The treering correlations show that the Colorado River's dependable yield is no more than 14 maf/yr and that there have been frequent and persistent droughts in the Basin. This indicates the importance of conserving water in an arid area in order to sustain beneficial uses over a long-term period that will include unpredictable and persistent droughts. Conclusions 1. The extremely high Colorado River flow in June and July, 1983, resulted from a combination of unusual weather events with a statistical probable recurrence even less frequent than once in a hundred years. 2. The Bureau of Reclamation did a fine job in coping with the unprecedented weather events and managing the Colorado River reservoirs during 1983. 3. Neither the Bureau nor anyone else could have predicted the unusually high flows in June and July early enough to have taken actions to prevent these damaging flows. 4. The current flood control regulations contain sufficient flexibility to allow the exercise of judgment (a) in determining the volume of flood control space above the minimum to be developed each January 1, and (b) in setting release rates above the minimum during the spring runoff periods. 5. The Bureau of Reclamation, the Corps of Engineers and the National Weather Service should work with the seven basin states and other interested parties to improve the river forecasts and river management, investigate channel capacity, and to determine if it is necessary to modify the flood control regulations. STATEMENT OF JACK L. STONEHOCKER, DIRECTOR, COLORADO RIVER COMMISSION OF MR. CHAIRMAN AND MEMBERS OF THE COMMITTEE, I APPRECIATE THE INVITATION TO APPEAR BEFORE YOU AND SUBMIT GOVERNOR RICHARD BRYAN'S POSITION CONCERNING THE FLOODING WHICH HAS BEEN OCCURRING ON THE COLORADO RIVER FOR THE LAST SEVERAL MONTHS. THE GOVERNOR IS EXTREMELY CONCERNED THAT THERE MAY HAVE BEEN FLAWS IN THE DATA GATHERING PROCESS, THE COMPUTER MODELING, THE INTERPRETATION OF THAT DATA OR THE RESPONSE TIME BETWEEN RECEIPT OF DATA AND IMPLEMENTATION OF HIGH RELEASES. THIS HAS OBVIOUSLY BEEN A VERY UNUSUAL YEAR WITH LATE HEAVY SNOW STORMS OVER THE MOUNTAINS WHICH FEED THE COLORADO, UNSEASONABLY LOW FOLLOWED BY A RAPID TEMPERATURES REMAINING WARMING PERIOD THAT SENT WATER CASCADING INTO THE TRIBUTARIES AND THE "MAIN" STEM OF THE COLORADO AT AN UNPRECEDENTED RATE. THE POINT IN QUESTION ISN'T WHETHER THE CONDITIONS WERE ABNORMAL, FOR THEY WERE, BUT WHETHER THE INVOLVED AGENCIES WERE EMPLOYING ADEQUATE TECHNOLOGY AND WERE MAKING PRUDENT MANAGEMENT DECISIONS. EACH AGENCY HAS DEMONSTRATED A SINCERE CONCERN ABOUT THEIR OWN PROGRAMS AND PERFORMANCE AND HAVE TAKEN STEPS TO EVALUATE THEMSELVES. IT IS HOWEVER DIFFICULT IF NOT IMPOSSIBLE FOR AN AGENCY TO BE PURELY OBJECTIVE WHEN EVALUATING THEIR OWN PROGRAMS OR PERFORMANCE EITHER INDIVIDUALLY OR COLLECTIVELY WITH OTHER AGENCIES. BECAUSE THESE QUESTIONS ARE OF IMPORTANCE ΤΟ SO MANY, BECAUSE INTERESTS ON THE RIVER ARE SO DIVERSE, AND BECAUSE SEVERAL AGENCIES ARE INVOLVED, IT APPEARS PRUDENT TO HAVE AN IN-DEPTH EVALUATION MADE BY A QUALIFIED INDEPENDENT ORGANIZATION WHICH CAN PROVIDE THE OBJECTIVITY THIS ISSUE DESERVES. THIS EVALUATION SHOULD AT LEAST INCLUDE ANSWERS ΤΟ THE FOLLOWING QUESTIONS: 1. ARE SNOW MEASUREMENTS TAKEN IN LOCATIONS WHICH ACCURATELY REFLECT THE CONDITIONS ON THE COLORADO RIVER 2. ARE ALL APPROPRIATE PARAMETERS MEASURED? 3. IS THE DATA GATHERED AT APPROPRIATE TIME INTERVALS? 4. DOES THE COMPUTER MODEL CONSIDER ALL APPROPRIATE DATA? 5. DOES THE COMPUTER MODEL PERFORM THE INTENDED TASK AS WELL AS POSSIBLE? 6. WERE THE APPROPRIATE MANAGEMENT DECISIONS RENDERED CONSIDERING THE DATA AVAILABLE? 7. WERE HIGH RELEASES MADE IN A TIMELY MANNER CONSISTENT WITH THE INFORMATION AVAILABLE.? IN LIGHT OF THE CURRENT SITUATION ON THE RIVER AND THE TIME WHICH HAS ELAPSED SINCE THE LAST REVIEW OF OPERATING CRITERIA, IT SEEMS APPROPRIATE THAT AS SOON AS AN INDEPENDENT REVIEW IS COMPLETED, A MEETING BE SCHEDULED TO REVIEW THE OPERATING CRITERIA. |