# The Biological Assessment and Rehabilitation of the World's Rivers: An Overview
## 2 Biological Assessment of Rivers  
### Africa  
The implementation and uses of bioassessment programs are diverse across the African continent. The ways bioassessment is used in Africa can be grouped into four broad categories: (i) setting management targets for rivers and monitoring for their compliance; (ii) monitoring the ecological conditions of freshwater ecosystems; (iii) monitoring in response to specific event/projects; and (iv) as part of water use license conditions. However, there are substantial overlaps between these bioassessments (Table S1). In South Africa, instream targets known as the resource quality objectives (RQOs) are set for every water body [19; 20]. RQOs are qualitative and quantitative descriptions of the physical, biological, and chemical attributes of a water body at the appropriate level of protection, after concurrent consideration of requirements for ecosystem functioning and socio-economic imperatives. Objectives are set for fish, riparian vegetation, and macroinvertebrate assemblages against which monitoring results are then interpreted for compliance. These objectives are mandated in the National Water Act of South Africa (Act  
Figure 1: Countries referred in this study regarding their status in biological monitoring and rehabilitation of rivers. No. 36 of 1998). Reference conditions for biological elements were set based on historical data sets, expert judgment, and data from minimally disturbed sites [21]. The River Ecostatus Monitoring Programme (REMP) is the official national bioassessment program in South Africa [22]. REMP is designed to generate ecological data to support the management of rivers and streams. Several formalized protocols, tools, and indices for the biological elements have also been developed [21; 23]. The fish, riparian vegetation, and macroinvertebrate assessment indices (the FRAI-[23], VEGRAI-[24], and MIRAI-[25]; respectively) are used for the routine ecological monitoring of rivers and streams. Each of these indices is composed of metrics, integrating biotic responses/preferences to alteration in the physical habitat, water quality, depth, shade/cover, and flow velocity. Results obtained through the indices are interpreted as the degree of deviations to reference condition, where A indicates no deviation/natural condition and F indicates the greatest deviation. Elsewhere within Southern Africa, protocols for ecological assessment have been developed based on macroinvertebrate assemblages: the South African Scoring System (SASS), the Zambian Scoring System (ZISS) [26], the Namibian Scoring System (NASS) [27], and the Okavango Assessment System (OKAS) [28; 29]. ZSS, NASS, and OKAS are modifications of SASS. SASS was originally modified from the BMWP (Biological Monitoring Working Party) and is presently in version 5 (SASS5) [30]. The results of these indices are expressed both as an index score (e.g., SASS5 score) and as an average score per recorded taxon (ASPT). There are also assessment protocols based on fish such as the Fish Assemblage Integrity Index (FAII) developed and used within the region [31]. In West Africa, recent studies have been directed towards establishing reference conditions for minimally disturbed sites using algae, macrophytes, benthic macroinvertebrates, and fish, which provide the foundation for bioassessment within the Sahel region [32]. Multimetric indices (MMI) based on macroinvertebrates-based were developed for the Zio River Basin (MMIZB; [33]) and to assess urban rivers within the Niger Delta region [34]. In Eastern and Central Africa, several biological assessment studies have been carried out mainly for scientific purposes. Indices of Biological Integrity (IBI) have been used to describe biological conditions in rivers based on macroinvertebrates (e.g., [35; 36; 37; 38; 39; 40; 41; 42; 43; 44], diatoms [45; 46; 47], and fish [48]). Other authors have explored trait-based approaches in Africa.