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. Electronic supplementary material The online version of this article (10.1007/s10661-019-7226-5) contains supplementary material, which is available to authorized users.

Uganda does not have a biomonitoring system for assessing the water quality of its rivers basing on benthic macroinvertebrates. An alternative system has been suggested in Tanzania. Differences in characteristics between Tanzania and Uganda may contribute to differences in the physical and chemical characteristics of rivers between the two countries, resulting in variations in macroinvertebrate assemblages and sensitivity levels in relation to disturbance. River Mpanga lies along the equator in western Uganda and shows heterogeneity of impacted and non-impacted sites along its course. The disturbance gradient of River Mpanga was determined using habitat integrity scores. The ability of the Tanzania River Scoring System (TARISS) to distinguish test from reference sites using macroinvertebrate assemblages was validated. Both qualitative and quantitative data were obtained through purposive sampling in both the wet and dry seasons. Macroinvertebrates were sampled following a slightly modified TARISS protocol. Canonical analysis of principle coordinates (CAP) showed that macroinvertebrate assemblages vary along a disturbance gradient, grouping test sites distinct from reference sites. Of the TARISS metrics, average score per taxon was able to distinguish between test and reference sites (p ¼ .009) among the TARISS metrics. Five taxa not included in TARISS were found in river Mpanga and were assigned sensitivity scores based on CAP predictive model in PERMANOVA. It was concluded that TARISS could be reliable for eastern African river systems but should be updated and/or modified by users in different regions to include missing taxa.

Hydroelectric power (HP) represents the main source of electricity in Africa, including the Democratic Republic of Congo. The demand for new dam construction is high, and major projects are currently progressing through planning and implementation stages. New HP dams should comply with both past and emerging environmental requirements. River systems need water to maintain hydraulic and ecological functions. Flow regime disturbance can prevent rivers from providing their ecosystem services and disrupt riparian communities. Most dammed rivers in Africa are understudied, however, in terms of their environmental flow requirements. This study analysed the hydrological regime and water quality of the Ruzizi River. The research investigated conditions of minimum water flow and hydropeaking at the Ruzizi I HP dam in terms of land management constraints and ecological impacts. According to Gumbel’s hydrological model, a discharge of ∼130 m3/s showed the longest return period (12 years) among the most recurrent flows. By contrast, the maximum recorded discharge of 143 m3/s showed a return time of 76 years. Any discharge between 46 and 120 m3/s could occur at any time within three years. The discharge–hydropower production relationship for the power plant provided a possible minimum environmental flow of 28 m3/s (i.e., 25%). Drinking water quality was assessed according to WHO water quality index (WQI) standards. Turbidity (i.e., total suspended solids) upstream and downstream of dams correlated strongly with rainfall (r = 0.8; n = 12) and land use. WQI values observed in excess of WHO drinking water standards indicate that the Ruzizi River is currently unsuitable for drinking water purposes.