Problems associated with the variability of southwest precipitation and seasonal snowpacks

The effects of variability in the general climate of Arizona are considerable on snowpack conditions and resultant runoff from major watersheds of the region. The limited predictability of these conditions exacerbates problems of surface water management. Long term planning for surface water resources and analyses of seasonal snow conditions must be based on a reporting scheme that considers appropriate definitions of normals.The precipitaton regime and snowpack conditions of Arizona can be characterized as consisting of many dry years interspersed by extremes of wetness. This kind of regime lends itself to employing measures such as the median as a representation of the most frequent or normal condition. The current reporting of snowpack and precipitation relative to the mean or average long term condition may misrepresent the interpretation of an individual yearly pattern in the context of the long term expected snowpack and precipitation climate of the Southwest region.