PUB Working Group 3 (WG3): Orographic Precipitation, Surface & Ground Water Interactions and their Impact on Water Resources

Objectives
The goal of this working group is to assess the reduction of uncertainties in hydrological predictions for ungauged basins based on improvements of important physical processes through land-atmosphere interactions. We will investigate the impacts of two particular physical processes on hydrological predictions and their implications on water resources management. These two processes play a very important role in predicting the land surface states such as soil moisture and snowpack. Specifically, we have the following three objectives:

• Improve the prediction of orographic precipitation and cold season processes in mountainous regions in climate models and estimate their impacts on hydrological predictions through hydrologic models and/or land surface models
  
  
• Improve the representation/parameterization of surface and groundwater interactions in land surface models and estimate their impacts on regional climate through land-atmosphere interactions
  
  
• Improve the management of water resources through improved predictions of snowpack and soil moisture based on improved representation of physical processes such as orographic precipitation, and surface and groundwater interactions

Objectives 1 and 3 � Orographic precipitation/season processes and water resources

• Study the effects of biases in estimates of orographic precipitation on land surface processes and hydrological predictions in mountainous regions.
  
  
• Compare predictions of orographic precipitation based on several models and examine the effects of spatial resolution and model parameterizations.
  
  
• Investigate the impacts of different orographic precipitation and hydrological forecasts on water resource management on weather and seasonal climate time scales.

Objectives 2 and 3 - Surface and groundwater interactions and water resources

• Develop and evaluate parameterizations of surface and groundwater interactions at spatial scales for land surface models and at basin scales for hydrological models, and investigates the impacts of such interactions on hydrological predications.
  
  
• Perform numerical experiments with a regional climate model coupled with a land surface model that includes the representation of surface and groundwater interactions implemented by Liang and determines the effects of such interactions on regional climate and hydrological cycle.
  
  
• Study the impacts of surface and groundwater interactions on water resource management.

The participants are adopting complementary approaches to achieve the objectives through integrated studies. The main outcomes of this working group are:

• The examination of various approaches for predicting orographic precipitation, their impacts on cold season processes such as snowpack, and effects on hydrological predictions and water resources management. Findings from these studies are especially relevant for hydrological predictions and managing water resources in basins with remote mountainous watersheds where observations are limited. These studies will be performed in basin(s) with dense networks of rain gauges and the working group will address the issue of uncertainties by examining their results based on observations at different rain gauge densities and different combinations of rain gauge, snotel or snow course, and stream gauges. Data assimilation using the snotel and/or snow course observations to reduce the uncertainties of hydrological predictions will also be investigated. These studies will initially be performed in the California and Pacific Northwest regions, and extended to other regions later.
  
  
• The development, testing, and application of a physically-based representation of surface and groundwater interactions, and investigations of the effects of such interactions on regional climate and hydrological cycle, and water resources management. These studies will be performed in semi-arid regions of the western U.S. where groundwater is an important source of water supply.

Key Participants:

• Xu Liang, University of Pittsburgh
• L. Ruby Leung, Pacific Northwest National Laboratory
• Dave Matthews, U.S. Bureau of Reclamation