**3. Results**

### **3.1 Aggregate indices and monitoring frameworks**

Indices may be simple or aggregate, that is, an index comprised of subindices. An example of the latter is the Aggregate Water Quality Index (AWQI). This was shown to have the capacity of being formulated without the problems of ambiguity (subindices show use-targeted acceptable water quality but the aggregated index fails to do so), eclipsing (aggregated index does not reflect sufficiently poor water quality shown by water quality variables), and rigidity (more variables have to be included targeted particular water quality aspects) as seen in Swamee and Tyagi [32]. To set up an AWQI, the process is as follows [33]:


The aggregation process ranges from the simple weighted additive method to the modified additive method [34] and more complicated methods [35].

An example of river condition index is the aggregate-type River Condition Index in New South Wales, which is comprised of the following subindices:

• "River Styles® (River [36]) Geomorphic Condition assessment – surrogate input under FARWH "Physical Form" category (RSGC)" [37].


The River Condition Index (RCI) score is computed by employing Euclidean distance for the subindices [38].

$$RCI = \mathbf{1} - \frac{\sqrt{(\mathbf{1} - RSC)\mathbf{2} + (\mathbf{1} - CDI)\mathbf{2} + (\mathbf{1} - HS)\mathbf{2} + (\mathbf{1} - RBCI)\mathbf{2} + (\mathbf{1} - RVC)\mathbf{2}}}{\sqrt{5}}$$

To interpret the results, **Table 1** converts metric to qualitative results using the Framework for Assessing River and Wetland Health (FARWH) [39].

The South African Government's River Health Program in the process of assessing both river health and stream condition developed an Index of Stream Geomorphology based on the measurement of geomorphic variables in view of the fact that they are the main constituents of the channel morphology impacting river aquatic biota [7, 40, 41]. This is comparable to the underlying logic in Chessman et al. [42] associating downward geomorphology changes with downward changes in assemblages of macrophytes and macroinvertebrates, while the latter are seen to display new sensitivities [43], a reaction seen also in freshwater mussels [44]. Also, positive result of fluvial geomorphology is associated with maintaining river health framework structural elements [45].

The River Habitat Quality survey framework as seen in Fox et al. [46] is used extensively worldwide, especially in Europe and the U.S., to assess both river health and condition. Its field survey protocols converge with those of SERCON (System for Evaluating Rivers for Conservation) [47] and was compared to the Systeme d'Evaluation de la Qualite du Milieu Physique (SEQ-MP) from France, and the field survey method of the Landerarbeitsgemeinschaft Wasser (LAWA-vor-Ort) from Germany [48]. A subset of its features leads to distinguishing between lowland, Alpine, and southern European rivers in terms of hydromorphological character [49]


### **Table 1.**

*Conversion of metric to qualitative results [37].*
