Tropentag, October 5 - 7, 2004 in Berlin "Rural Poverty Reduction through Research for Development and Transformation"

Simulation and Validation of Modelled Water Use and Biomass Production of Natural Plants in the Draa Valley (Southern Morocco) - A Case Study of Impetus Testsite Taoujgalt

University of Bonn, Institut of Plant Nutrition, Germany

Abstract

Southern Morocco is a semiarid, heavily grassed region with a long tradition of transhumance activity. The spatial ecosystem model SAVANNA, developed by M. Coughenour, is being used to model ecosystem dynamics and to gain knowledge about the thresholds of sustainable use in this region. Within SAVANNA different functional groups of vegetation are defined to simulate plant growth and plant competition for nutrients and water. In addition, biomass intake by animals and the movement of herds are simulated.
Parameterisation and calibration of the SAVANNA model for the Draa watershed as well as first simulation results will be presented, considering sheeps, goats and camels as the most abundant animals. For the plant part of SAVANNA, transpiration measurements as well as biomass determination are being used, which were carried out in the years 2001 - 2003 in order to achieve an estimate of the plant influence on the hydrological circle of this water catchment. Intensive measurements took place in a characteristic rangeland area of the nothern Draa valley at Taoujgalt (1900 m a.s.l.), located at the southern slope of the High Atlas mountains with a homogeneous plant cover. The dominant perennial species are Artemisia herba-alba and Teucrium mideltense
Biomass production and plant transpiration in this region are less linked to local precipitation, and may even exceed precipitation. This indicates the influence of local water storage in the soil, and/or the influence of groundwater fluxes within this mountainous region. As well it is important to comprise that the goundwater level of this area strongly depended on local precipitation, due to the well irrigation systems of farmers in the nothern part of Taoujgalt area.

Keywords: Biomass, desert, plant modelling, precipitation, south Morocco, transpiration rates, water use

Contact Address: Frank Gresens, University of Bonn, Institut of Plant Nutrition, Karlrobert-Kreiten Str. 13, 53115 Bonn, Germany, e-mail: fgresensuni-bonn.de