| Winter snowfall in mountainous regions and the subsequent spring and summer melting of the snowpack are critical components of the water supply throughout many areas of the world. Melting snowpacks serve to recharge reservoirs, which in turn are used for agriculture and civic allocation. Understanding the processes controlling the evolution of the snowpack in specific watersheds is of importance to those charged with the responsibility of managing reservoir systems.; Much of the current state of snow research is based on areas that have consistently high snowfall amounts. Little has been done in arid climates such as Arizona. The goal of this dissertation was to determine how the evolution of the snowpack in an arid climate differs from other regions and how an understanding of those differences could aid in the modeling and simulation of the snowpack evolution and melt water generation. The three pathways for answering these questions were a quantitative, model-based assessment of the snowpack at a research station in Arizona, a synoptic atmospheric analysis of the controlling factors for the snow ablation, and simulation of the runoff generated from the snowmelt.; Differences in the evolution of Arizona's snowpack relative to other regions were found using each of the three pathways. Losses of snow water equivalent to the atmosphere ranged from 3.8% to 24.5% during different ablation periods within the melt season. Within the energy budget of the snowpack, the relative importance of the net radiative flux was smaller than the sensible heat flux compared with results from other regions. Not surprisingly, conditions for high snow ablation rates necessitated atmospheric circulation that produced southerly winds, warmer temperatures, and higher pressures. This type of circulation occurred later in the snowmelt period. Successful simulation of the runoff associated with snowmelt revealed differences in many of the parameters relative to other modeled basins. These differences included the trend, timing, and magnitude of the runoff coefficients, recession coefficients, and degree day factors. Results suggest that a future forecast model of runoff associated with melting ephemeral snowpacks in arid regions is a realistic proposal. |
