Biological water quality assessment in the degraded Mutara rangelands, northeastern Rwanda

Marie-Claire Dusabe,Torsten Wronski,Guilherme Gomes-Silva,Martin Plath,Christian Albrecht,Ann Apio

doi:10.1007/s10661-019-7226-5

Abstract

Rwanda is a heavily overpopulated country that also suffers from overstocking with livestock, especially following the return of war refuges after the civil war (1991–1995). At present, approximately 20% of the human population in Nyagatare District in northeastern Rwanda has no access to clean drinking water and sanitation. We used a biotic index based on the presence of selected families of aquatic macroinvertebrates, derived from the “Tanzania River Scoring System” (TARISS), to assess water quality at N = 55 sites in the Mutara grasslands in Nyagatare District. Poor water quality became evident across most sampling sites both in the Muvumba (mean ± SE TARISS score 5.25 ± 0.10) and Karangazi Rivers (4.79 ± 0.12). Using a general linear model, we asked whether direct effects of land use forms and input of anthropogenic wastewater have an impact on water quality. Our results found no immediate effects of both forms of disturbance/pollution, probably because overall water quality was already poor. Our study is intended to serve as a starting point for continuous monitoring of water quality in the Mutara rangelands in NE Rwanda. The method applied here is cost-efficient, requires only basic equipment, and training local students to apply this technique can provide a solid basis for its implementation in future surveys related to public health.

Highlights

Safe and freely available water is a vital and indispensable resource for humans and their livestock
Our major aim was to provide an overview of water quality in our study area and to contrast our findings with assessments that were based on a few physico-chemical parameters only (RNRA 2014), driven by the fact that the surface waters we considered in this study represent a source of drinking water for a large portion of the local human population
Following Aquilina (2013), our biological water quality monitoring based on averaged the BTanzania River Scoring System^ (TARISS) scores characterized water quality in both river systems as Bpoor^, as mean (± SE) scores were determined as 5.25 ± 0.10 for the Muvumba and 4.79 ± 0.12 for the Karangazi River (Fig. 2)

Summary

Introduction

Safe and freely available water is a vital and indispensable resource for humans and their livestock. 884 million people, i.e., 12% of the global human population, lack a basic drinking-water service (freely available, clean drinking water within a radius of 30 min walk), including 159 million people who are entirely dependent on surface water (WHO 2017). In Rwanda, settlements and farms are often located along valley slopes where water run-off flushes manure, human excretions, and waste water into rivers and streams, leading to increased levels of dissolved nitrogen. These agricultural and domestic activities pollute the surface water and lead to eutrophication and serious public health issues in large parts of Rwanda (Sekomo et al 2012)

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Conclusion