Impacts of Climate Change and Land Use on the Southwestern United States
Coping with Severe Sustained Drought in the Southwest

What management alternatives might help?

Abstracted from Booker (1995), Henderson and others (1995), and Lord and others (1995)

Studies of impacts of a hypothetical Severe Sustained Drought on the Colorado River indicated that:

  • Even the progressively deepening, 19-year, worst-case, Severe Sustained Drought developed from treering analyses was not enough to completely drain the reservoirs of the Colorado River system. However, users in both basins would be impacted.

  • The Upper Basin is more vulnerable to impacts from a severe drought than is the Lower Basin.

  • Non-consumptive and environmental water uses are more vulnerable to drought under the current Law of the River than are the consumptive uses.
  • Grand Canyon

    Figure 9. Grand Canyon
    (Photo by Mike Bucheit)
    Lord and others (1995) discuss alternative approaches that could be used to reduce drought damages or to spread them more equitably. Two alternatives that did not effectively reduce overall damages (in their role-playing simulations) but which might ensure greater equitability were:

    Other alternatives proved quite effective in reducing damages:

    Headwater storage changes could reduce drought impacts by about 25%. A similar improvement was obtained (in simulations) from water banking and marketing alternatives. The following figures show the reductions in drought damages simulated by Booker (1995). Interstate marketing effectively reduced damages in all years; banking reduced damages during the worst drought years.

    Economic damages sustained under the Severe 
Sustained Drought scenario

    Figure 10. Economic damages sustained under the Severe Sustained Drought scenario, from consumptive uses (top) and from consumptive and non-consumptive uses (bottom), with and without interstate water marketing. (Modified from Booker,1995)

    comparison of damages with and without water banking

    Figure 11. Same as Figure 10, but showing damages with and without water banking. (Modified from Booker, 1995)

    These alternatives would require changes in the Law of the River to greater or lesser extent. Such changes are difficult in practice and, even in their role-playing exercises responding to the Severe Sustained Drought, only minor rule changes could be achieved, unless water banking or marketing transactions were allowed.

    Lord and others (1995) concluded that management changes that could be accomplished within the individual states were generally more promising, because they could be quite effective (especially where they reduced demands overall) and because they could be accomplished with greater flexibility and speed than changes to the Law of the River. Such within-state management decisions were quite useful during the recent California drought and have long been useful in Colorado. If concentrated in the Upper Basin, within-state management changes were particularly effective.

    Considering the severity and duration of the drought considered in these studies, the analysis of severe sustained drought on the Colorado River Basin suggests that tremendous resilience has been stockpiled through the construction of the massive reservoir system on the river as well as through the Law of the River which organizes interstate water management there. Many other regions and rivers might not fare as well under such a drought. At least some aspects of the Law of the River, however, are rigid in ways that might result in an unequal distribution of drought impacts, with the Upper Basin states and non-consumptive uses being most vulnerable. The most successful alternatives seem to require greater flexibility for managers of the Colorado River water-resource systems to cope with long-term droughts. Such flexibility would probably also be necessary if the system were faced with long-term climate change.

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