and the implications of weather modification. The last subject mentioned includes relevant aspects of ecology, economics, law, political science, and sociology.

Evaluation of State Operational Programs

Several States have weather modification programs supported by tax dollars. These operational projects are carried out on a non-randomized basis in contrast to some of the more elaborate, statistically designed Federal experiments. In many cases these State programs must be evaluated to show their effectiveness, so that public support will continue. This section discusses a few program evaluations.

An initial evaluation has been made of the target area rainfall for the Colorado River Municipal Water District (CRMWD) cloud seeding activity north and east of Big Spring, Texas (Girdzus 1976). The project aircraft dispensed silver iodide by igniting nonejectable pyrotechnic flares below cloud base; updrafts dispersed the chemical into the clouds. Seeding was concentrated in areas showing evidence of supercooled water but was not carried out in those cells showing dissipation or glaciation. Analyses of raingage and climatological rainfall data indicated that, during the project operational period 19711975, the target area received more rainfall than in any other fiveyear period since 1941. Preliminary findings for the 1971-1975 period also indicated that rainfall was 25 percent greater over the target area than the control area. In addition, rainfall measured by the CRMWD gages suggested a substantial increase in precipitation during the seeded period. Although the results of the study tend to indicate that rainfall over the target area had been increased, the author notes the uncertainty in directly relating cause and effect.

A large-scale precipitation modification experiment has been proposed for part of southern Illinois. In this connection, measurements of background concentrations of silver (Ag) were made in the expected target area (Gatz 1975). An assessment of present conditions will provide a basis for comparison with Ag concentrations in precipitation during any future cloud seeding operations that use silver iodide (AgI) as the seeding agent. Such comparisons would help to identify precipitation treated by seeding material and thus would aid in evaluating the efficacy of the seeding and the locality of the effect. Analysis of unseeded precipitation samples in Illinois showed background Ag concentrations somewhat higher than those found in unseeded precipitation in other parts of North America. These higher concentrations were felt to be due largely to the greater relative contribution of windblown soil dust in Illinois as compared with western mountain regions.

Evaluation of weather modification experiments and operations is difficult, and various methods of measurement and analysis have been used in attempts to obtain definitive proof of the effectiveness of cloud seeding. Changnon and Morgan (1975), for example, performed a statistical evaluation of the results of the first 4 years of a two-county

hail suppression project in Texas. They examined hail and crop-hail insurance data from seeded counties and adjacent non-seeded counties and found loss costs (loss divided by liability) to be the best single measure for evaluating success. Most of the data examined strongly suggested that the hail suppression was successful for the 4 years 1970-1973. The best estimate of the magnitude of the reduction in loss costs due to the seeding activity was 48 percent. Loss cost normalizes the losses to fluctuations in the liability which can be large.

Public acceptance of cloud seeding in South Dakota has been carefully monitored since before the large-area State program began in 1972. Preliminary findings have been reported from a social survey conducted in 20 counties during September 1974 (Farhar 1975). The author found that favorable attitudes toward the technology continued to be the majority perspective after three seasons of operation. However, a large minority still espoused the religio-natural orientation. Belief in the effectiveness of cloud seeding for suppressing hail increased while the proportion believing it effective for rain enhancement, the majority, had fallen off 10 percent. The majority of the sample favored the State program and about a third thought that they had derived economic benefit from it. An evaluation of the seeding effectiveness of South Dakota's multicounty weather modification program has been published (South Dakota Division of Weather Modification 1976). Computer analyses of over 300,000 rainfall and crop-hail insurance records were made for seed and no-seed years. The monthly rainfall data analysis showed that seeded county rainfall overall exceeded the unseeded county rainfall by 6.7 percent during seeded years (1972-1974), with the probability of 7 percent that the result occurred by chance. Analysis of the crophail insurance data indicated that South Dakota fared very well in terms of crop-hail damage during seeded years as compared to previous Furthermore, the seeded counties fared better than would be expected from unseeded county performance, with the probability of 6.5 percent that such favorable results occurred by chance. The analysis also showed that it was unlikely that hail suppression was bought at the expense of rainfall in the participating counties.

In a separate study, Dennis et al. (1975) evaluated the effects of cloud seeding on growing season rainfall in North Dakota. Rainfall data collected at 67 gages in a 2750 mi target area during a four-year ranmi2 domized cloud seeding experiment were stratified in a variety of ways and subjected to several kinds of statistical tests. The authors tentatively concluded that dynamic effects, including rainfall increases, were produced by light to moderate silver iodide seeding from below cloud base. The potential rainfall increase resulting from seeding below selected clouds on days with dynamic seedability was estimated at one inch per growing season.

Legislation

No new Federal legislation on weather modification was enacted during 1975, but several proposed bills will reach the hearing stage in 1976, and, if enacted, would influence greatly the direction and content of

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future weather modification activities. At the State level, North Dakota created a Weather Modification Board to regulate and operate the weather modification activities in the State. Idaho, Oregon, and Texas made some changes in their statutes, regulations, or procedures.

The Congressional Subcommittee on International Organizations of the Committee on International Relations met on July 29, 1975, to consider House Resolution 28, which calls for the U.S. Government to seek an agreement with other members of the United Nations on the prohibition of research, experimentation, or use of weather modification activity as a weapon of war. Representative Gilbert Gude of Maryland and Dr. Gordon J. F. MacDonald of Dartmouth College, the only witnesses heard, testified in support of the resolution. No other major action on this matter occurred during the year.

During his testimony, Mr. Gude noted an exchange of letters between three members of the Congress and the Executive Department (Subcommittee on International Organizations 1975). In response to a recommendation by the Congressmen for a coordinated program in weather modification by a single civilian agency, Mr. Norman E. Ross, Jr., Assistant Director of the Domestic Council, presented the Administration's views on the Federal role in this technology. His letter expressed the belief that a program under one agency's leadership was neither necessary nor desirable; that the Interdepartmental Committee on Atmospheric Sciences (ICAS) was a coordinating group; and that, within ICAS, a series of lead agencies had been established to concentrate efforts in particular areas. An important point in the letter was that an agency charged with the responsibility for dealing with a particular national problem should be given the latitude to seek the best approach or solution. In some instances, this may involve a form of weather modification.

A bill, H.R. 2742, was introduced on February 4, 1975, "to assure that weather modification activities and the collection of hydrometeorological information necessary to the management of water resources can be conducted in conjunction with the management and administration of wilderness areas and other Federal lands". The proposed legislation was referred to the Committee on Interior and Insular Affairs. No public hearings were held.

Another bill was introduced in the House of Representatives on October 6, 1975. H.R. 10039 would provide that the Secretary of Commerce carry out a research and development program, set up a weather modification information system, institute, a control and reporting system, and maintain a register of qualified weather modifiers. No hearings on this legislation were scheduled during 1975.

In the Senate, Senator Bellmon of Oklahoma introduced three bills, S. 2705, 2706, and 2707 on November 20, 1975. The first bill would have the Secretary of Commerce establish a National Weather Modification Commission to assess the many aspects of this technology. The

second bill would require that the Secretary of Commerce carry out a ten-year experimental research effort to determine the effectiveness of weather modification techniques in decreasing the impact of drought. The last bill would authorize the Secretary of Commerce to carry out a program of assistance to States in preventing and alleviating drought emergencies. These bills were referred to the Committee on Commerce.

Legal Actions

There have been about a dozen lawsuits since the 1950's affecting planned, on-going, or completed weather modification activities (Davis 1974). Four cases arising in 1974 and 1975 are described in this section.

Davis and St. Amand (1975) reported on recent legal actions involving weather modification activities. The case, Montana Wilderness Association v. Hodel, challenged the issuance of a permit for seeding in the area of Hungry Horse Dam, Montana. However, the operational project was cancelled because adequate precipitation became available for the Bonneville Power Administration's needs. Later, in the summer of 1974, the court dismissed the case as moot because there was no longer any "case or controversy".

In June 1974, a hearing was held at Littlefield, Texas, on the case, Farmers and Ranchers for Natural Weather v. Atmospherics, Inc. The plaintiffs had filed a motion for a temporary injunction to halt seeding intended to increase rainfall and decrease hail. Their argument was that Texas courts had adopted the position in prior cases that landowners were entitled to whatever precipitation would fall naturally on their property, an implication that seeding would decrease such precipitation. However, experts testified that there had been no diminution of precipitation resulting from the seeding. In addition, lawyers for the defendants argued that more recent regulatory legislation had superseded the language in those cases. The judge ruled for the weather modifiers.

In another action, a jury trial was held in 1974, at Caro, Michigan, in the case of Reinbold v. Sumner Farmers, Inc. and Irving P. Krick, Inc. The plaintiff's complaint for damages, an injunction against further seeding, and an order declaring the suit to be a class action was filed in 1972. The judge ruled against the claim for an injunction; the jury did not sustain the plaintiff's claim for damages. At a prior hearing, the motion to treat the case as a class action was denied. Davis and St. Amand discuss the issue of legal causation as the crux of this trial and other weather modification litigation in which the plaintiff seeks recovery of damages for his losses. They point out that a defendant can win such a lawsuit by prevailing on that single point. Another conclusion, they make, is that the use of expert testimony is essential for the defendant as it is most persuasive to jurors as well as to judges. The authors also note that prior assertions of effectiveness by cloud seeders can and will be used against them by litigants.

A disastrous flood occurred in the area of Rapid City, South Dakota on June 9, 1972. Three years later, a class-action suit was filed against the Department of Interior (DOI) for hundreds of millions of dollars in damages. The plaintiffs claim that cloud seeding, sponsored by the DOI's Bureau of Reclamation, contributed to the flood (Hacker 1975). No further information has emerged in the press on the status of this lawsuit.

As a guide to the planning and execution of future weather modification programs, an initial attempt has been made to define what proof various States may require to grant a water right based on water developed through such programs (Jones et al. 1975). The authors developed generalized hydrologic and engineering guidelines for preparing claims, even though they recognized the difficulty, if not impossibility, at this time to provide unquestionable proof that additional water was created as a result of weather modification. As part of the study, an evaluation of a cold orographic weather modification program was made, using an atmospheric model interfaced with a runoff simulation model. Several State water resources officials were interviewed and their opinions furnished valuable input. Jones et al. concluded that the right to appropriate water arising from weather modification might properly rest with the individual States (as it does in Utah, for example) and that hydrology has seldom been used to its fullest extent in the evaluation of weather modification.

International Activities

Many countries have undertaken or have an interest in research on or the application of weather modification. Much of this activity is coordinated through the World Meteorological Organiztion (WMO). The actions of the WMO and other entities are discussed herein.

During 1975, the Seventh Congress of WMO adopted a Weather Modification Program containing several important features (World Meteorological Organiztion 1975). As part of the program, the WMO initiated an annual inventory of national activities related to weather modification beginning with CY 1975. Member nations were requested to complete a questionnaire for each of their projects and to supply the texts of any appropriate national or local laws. Information from 16 countries reporting their activities will be compiled and published by the WMO and will provide an authoritative reference on the world's weather modification activities for the year.

In addition to the register of activities, the WMO began to plan for an international Precipitation Enhancement Project (PEP). Objectives of the project are as follows: