University of FloridaDepartment of Agricultural & Biological Engineering

Development and Evaluation of a Modeling Framework to Assess Hydrological and Fish Population Impacts of Development in the Okavango Basin in Africa

Participants: Anna Cathey, Rafael Muñoz-Carpena, Dr. Gregory A. Kiker (UF)

Timeline: 2009 - 2011

Funding Agencies: NSF-IGERT, NASA-LCLUC

Project Summary

The Okavango Basin is a large and exceptionally pristine transboundary catchment in southern Africa that empties into the Okavango Delta. The Okavango Delta is a large inland delta that spreads out on the flat and dry Kalahari sands of Botswana and is evapotranspirated before ever reaching the sea. Threats to the integrity of the system loom as Angola emerges from a devastating civil war and climate change predictions forecast increasing temperatures and as yet unknown shifts in precipitation. This situation calls for a thorough understanding of hydro-ecologic responses to future scenarios of change. Hydrologic models in the area have been developed and calibrated but little work has been done concerning the reliability of these models or how the models may affect the ecology of the system. This work is twofold involving a global sensitivity and uncertainty analysis on the existing hydrologic models in the area as well as the development of a fish population model for the Okavango Delta based on the hydrologic models and the flood pulse concept.

Uncertainty analysis is useful for measuring model reliability and sensitivity analysis can be used to identify the parts of a system that need to be better understood in order to produce better models. Global sensitivity and uncertainty analysis (GSA/GUA) techniques sample throughout the multi-variate parametric space and are especially useful when considering complex nonlinear models. In this work a methodology is used to optimize computational resources while at the same time conduct a robust GSA/GUA. In this method the qualitative Morris GSA Method is first used to reduce the number of important inputs so that the quantitative and more computationally intensive variance based FAST method can be run on a subset of important parameters. The GSA/GUA is run on the Pitman rainfall runoff model of the upstream Okavango Basin and the HOORC reservoir model in the downstream Okavango Delta. Results show that in the upstream basin the most important processes concern inputs regarding:

  1. groundwater recharge
  2. the ratio between potential and actual evapotranspiration
  3. soil moisture storage

The hydrology of the Okavango Delta is driven by an annual flood pulse from the rains in upstream Angola. This flood pulse is proposed to be an important driver in the fish populations. The second portion of this work involves the development of a fish model built upon the Flood Pulse theory as well as Foraging Arena. The Flood Pulse theory states that is a “first flush” effect at the onset of the flood, which results in a release of nutrients. Resting zooplankton eggs hatch when they are submerged by the floodwater and feed on the plentiful phytoplankton and other food sources provided by the burst in primary production. Fish spawning rates then increase at this flood edge so that the fry can feed on the abundant zooplankton. Foraging Arena asserts that fishes make spatial decisions in order to minimize predation. The resulting fish model will be compared to data to understand the degree to which these theories explain fish population dynamics.

Anna Cathey
Anna Cathey visits a borehole in the Okavango Delta, Botswana.

Living with Thirst

Six students from a variety of disciplines but with a common research interest in southern Africa collaborated from to produce the video, Living with Thirst: People and Wildlife in Southern Africa's Variable Climate for the Ecological Society of America's Millennium Conference (2009). The video fuses insights gained from a diversity of departments, backgrounds, field experiences, and world views to produce a holistic picture of the relationship between people, water, and wildlife in a dry and unpredictable climate. Two students from ABE were involved in the production and are proud to be a part of the story that is told.


Conference Papers

  • Kiker, G.A., R. Muñoz-Carpena, P. Wolski, A. Cathey, A. Gaughan, J. Kim. 2008. Incorporating Uncertainty into Adaptive, Transboundary Water Challenges: A Conceptual Design for the Okavango River Basin[2.49MB]. Int. J. of Risk Assessment and Management 10(4):312-338.
  • Vellidis, G., P. Barnes, D.D. Bosch, & A.M. Cathey. (2006) Mathematical simulation tools for developing dissolved oxygen TMDLs. Transactions of the ASAE 49(4): 1003−1022.
  • Cathey, A.M., G. Vellidis, M.C. Smith, R. Lowrance, & R. Burke. The calibration, validation, and sensitivity analysis of Georgia DoSag: An in-stream dissolved oxygen model. (Total Maximum Daily Load). Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005 701P0105.
  • Worley, J.W., M. Czarick & A.M. Cathey. (2002) Ammonia emissions from a commercial broiler house. Paper No. 024118 in Proceedings from 2002 ASAE Annual International Meeting/CIGR XVth World Congress, Chicago, Illinois.


  • Cathey, A., Muñoz-Carpena, R, Hughes, D. 2010. Global Sensitivity Analysis of the Pitman Rainfall Runoff Model in the Okavango Basin. Presentation at the Flood Pulse Symposium, University of Botswana. Maun, Botswana.
  • Parent, G., A. Cathey, A. Gaughn, W. Kanapaux, D. Wojick. 2009. Living with Thirst: People and Wildlife in Southern Africa's Variable Climate. Video case study for the Ecological Society of America Case Millennium Conference. Athens, Georgia.
  • Cathey, A., R. Muñoz-Carpena, P. Wolski. 2009. Global Uncertainty and Sensitivity Analysis of Hydro-Ecologic Models of the Okavango Basin, Botswana. Presentation at the University of Botswana Harry Oppenheimer Research Center. Maun, Botswana.
  • Cathey, A., R. Muñoz-Carpena, G. Kiker. 2009. Uncertainty Analysis Using the Method of Morris on a Hydrologic Model of the Okavango Basin, Botswana. Presentation at the AWRA Summer Specialty Conference: Adaptive Management of Water Resources II. Snowbird, Utah.
  • Cathey, A., R. Muñoz-Carpena, G. Kiker. 2009. Uncertainty Analysis of a Reservoir Model in the Okavango Delta, Botswana. Presentation at the Florida Section ASABE. Daytona Beach, Florida.
  • Cathey, A.M. (2001) Development of West Nile surveillance program in Chatham County. Presentation for the Mid Atlantic Mosquito Control Association Conference. Savannah, Georgia.


  • Cathey A, Kiker, GA, Muñoz-Carpena,R. (2008) Incorporating Uncertainty into Adaptive, Transboundary Water Challenges: A Conceptual Design for the Okavango River Basin. Poster presented at University of Florida Water Institute Symposium, Gainesville, Florida and NSF IGERT Sustainability Conference, Fairbanks, Alaska.
  • Cathey, A.M. (2004) Modeling dissolved oxygen in Coastal Plain Georgia streams. Poster presentation for the American Society for Agricultural Engineers Conference. Ottawa, Canada.

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This page was last updated on July 13, 2019.