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Summer 2000 Bulletin
Costilla: Stage Set for Possible Lawsuit
The first problem on the Costilla is the water-allocating 1940s Costilla Compact itself. It specifies a maximum diversion rate into the rights-wealthy Cerro Canal which, if applied continuously throughout the season (as tends to happen), results in diversions far above the 'duty of water' calculated by the engineer advisors who actually worked out the details behind the Compact. In a dry year like 1996 and the present one, continuous maximum diversions mean that little or no water gets past the Cerro diversion in the irrigation season; the river aggrades and dries up, there is no water to replenish the shallow aquifer and the bosque that depends on it, and no downstream irrigation is possible. In 1996 the downstream acequias got only 2% of the Costilla supply, the rest taken from the river at the Cerro diversion dam. Although the Cerro irrigators may genuinely utilize all the water diverted in the hot, dry middle of the year, diversions well beyond demand almost certainly take place early and late in the irrigation season - the proof of the pudding being the artificial wetlands that have developed at the ends of the diversion system. The Compact Commission is beginning to recognize that waste, the result of over-diversion, may be occurring. If the legal argument can be successfully made that the engineer advisors' limitation of Cerro diversions to pre-Compact demand is implicit in the Compact, the wasted water can be returned to the Costilla and Garcia water right owners and the river ecosystem. This precedent-setting legal question is presently being tested elsewhere in the West. The Costilla Commission have not been responsive to out-of-court legal pressures on this issue, and a lawsuit may be needed to get them to take real action. A second problem, and opportunity, on the Costilla is the changes that have occurred as a result of the recent improvements to the two major dams in the system. Under both Colorado and New Mexico law (the Costilla is an interstate stream), you can't increase your depletion right by improving storage or diversion efficiencies, which has been achieved by re-engineering the Costilla and Cerro dams over the past two decades. Over that period, Cerro diversions have increased substantially. The complicating factor is that 'supplies' of Costilla water upstream of the diversion have also increased over the same period. To make the case that the increased diversions have partly resulted from the dam improvements, it will be necessary to tease out the different contributions to supplies made by natural and man-made factors. Amigos Bravos is presently looking for a hydrologist to start performing this analysis, and to work with our Costilla lawyer, Peter White. If we find that significantly increased diversions have resulted from the changes to the dams, it may be legally possible to limit storage and diversion by tying them to historic efficiencies and use. This would effectively replace the former leakage (3 cfs at both structures), to the great benefit of the river system and irrigators downstream and the Rio Grande Cutthroat fishery upstream.
Readers will by now be familiar with problems on the Rio Costilla, which indeed are a microcosm of water allocation problems throughout New Mexico: increased upstream diversions and appropriations threaten traditional acequias, along with instream values and bosques, while 'frontier' laws designed to encourage water exploitation and development are ill-equipped to cope with the need to share a fully developed resource and provide for 'new' values such as environmental ones.
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