Development and use of integrated wetland condition index for lacustrine fringe wetlands of Lake Tana, Ethiopia

Abstract

The primary objective of this research was to develop an integrated wetland condition index (IWCI) for lacustrine fringe wetlands (LFWs) in Lake Tana, Ethiopia, which has been highly impacted by recessionary agriculture, water hyacinth infestation, and both short- and long-term water level fluctuations (WLFs), as well as a heavy sediment load. The index of lacustrine wetland condition was developed based on four wetland characteristics that define wetlands: hydrology, water quality, sediment quality, and wetland biota. The value obtained from field and laboratory measurements of each wetland hydrology, water chemistry, and sediment characteristics indicator was normalized by allocating scores based on literature information and the results of this research project from three different disturbance-level lacustrine wetlands in Lake Tana. Macrophyte, diatom, and zooplankton indicator species tests (IndVal% and p (raw)) were calculated using PAST (PAleontological STatistics). Scores were allocated on a scale from 1 to 10, in such a way that the highest scores reflected the best conditions and the lowest scores the most disturbed and unhealthy conditions. Within four sub-indexes, there is more than one measure, with each measure given equal weighting, whereas the four wetland components (hydrology, water chemistry, sediment, and biota) are weighted as per their contribution to the overall wetland condition. Weights were assigned using the Decision Support System Software of DEFINITE. Finally, the total IWCI was classified into five wetland condition categories, namely: very poor or very far from the reference (0-3), poor (3-5), moderate (5-7), good (7-9), and excellent wetland condition or reference condition (9-10). According to the IWCI of the low water level period, eight wetland sampling sites were found within a moderately impacted condition (44.44%); similarly, eight wetland sampling sites were found within a good or mildly impacted condition; and only two wetland sampling sites (11.11%) were found in an excellent or reference condition. Thus, this IWCI developed and tested in this study could be a powerful tool to inform decision-makers on lacustrine wetland conservation and restoration priorities throughout the Lake Tana Ecosystem.