Date of Award

Spring 1991

Project Type


Program or Major


Degree Name

Doctor of Philosophy

First Advisor

Berrien Moore, III


The subject of this dissertation is the terrestrial water cycle and development of tools to study the issue of global hydrologic change. A rationale is developed to study the water cycle at regional and continental scales using macro-scale hydrology models coupled to Geographic Information Systems (GIS). A linked Water Balance/Water Transport Model (WBM/WTM) was constructed and tested as part of this research. The model was applied to two tropical river systems, the Amazon River in South America and the Zambezi River in southern Africa.

The WBM/WTM is a distributed parameter model, operating at 0.5$\sp\circ$(latitude x longitude) spatial scale and with monthly timesteps. The WBM transforms spatially complex data on climate, vegetation, soils and topography into predictions of soil moisture, evapotranspiration and runoff. The WTM uses computed runoff, information on fluvial topology, linear transfer through river channels and a simple representation of floodplain storage to generate monthly discharge for any cell within a simulated catchment. For the Amazon, WBM/WTM results were checked against established data sources and found to be in good agreement. The Zambezi simulation was more problematic. This study identified and corrected errors in the precipitation, potential evapotranspiration, and soil water capacity data sets, and demonstrated the importance of checking such calculations against reliable discharge data. Simulations with data from the Amazon and Zambezi River systems identified fluvial transport parameters which best matched observed discharge. Similar parameters captured the dynamics of river flow in these strikingly different river systems. This suggests that large tropical rivers may have convergent properties that can be modeled using simple algorithms.

This work produced a set of calibrated, macro-scale hydrology models for two large rivers prior to significant anthropogenic disturbance. Such simulations are prerequisites to the study of hydrologic change. The major impacts of such change, from shifting land use, climate change, and water resources management, can be simulated using macro-scale hydrology models. The dissertation offers a strategy to accomplish this goal.