14 - Contribution to the groundwater hydrology of the Amboseli ecosystem, Kenya

Summary

ABSTRACT The Amboseli ecosystem consists of the basement plains, the lacustrine saline plains with fresh water swamps and the volcanic slopes of the Kilimanjaro. The area is well known for its large and varied population of wild herbivores, supporting a large tourist industry. The two major fresh spring zones sustaining some 20 km² of swamps and an additional 16 km² of wet areas chiefly covered by grass, belong to the relatively shallow part of a regional groundwater flow system in the volcanic complex. A 7.5 m rise of the groundwater table since the 1960s and the recent expansion of one of the swamps has caused concern. The rise cannot be explained by the available rainfall data and may be related to more frequent runoff, because of overgrazing, in the catchment feeding episodically the seasonal Lake Amboseli. In addition, tectonic movements may have increased the outflow of the the deeper diffuse part of the flow system.

The dynamics of the swamps have been studied. Available data suggest that no major changes are likely to affect the swamps in the near future. A good proportion of the annual recharge of the springs, about 14 % of the estimated rainfall, takes place in the Tanzanian part.

INTRODUCTION

The Amboseli ecosystem can be characterized as a semiarid savanna environment, which shows considerable spatial and temporal variation in resources; climate, soils, vegetation and hydrology. This has an important bearing on the structure and functioning of the ecosystem and has important consequences for the management. The area is well known for its large and varied population of wild and domestic herbivores, upon which a large tourist industry is based.