**6. Discussion**

In this study, water quality was examined using chemical, physical, and biomonitoring methods. In chemical analysis, different parameters were tested, such as magnesium, chromium, aluminum, copper, cadmium, dissolved oxygen (DO), nitrogen (N), and phosphorous (P) [42]. Physical parameters include pH, total suspended solids (T.D.S), conductivity, chloride, sulfate, nitrate, calcium, total hardness, sodium, and potassium. In bio-monitoring FBI, EPT, ASPT, and BMWP were calculated to determine water quality.

The concentration of metals was almost normal but some of them were high such as cadmium, sodium, potassium, and chromium. The pH values were low at the start and exceeded in site D. This shows that Organic influx wastage in the monsoon season may lower the water pH at that site D. The pH affects the biochemical process as well. It also indicates water quality and the extent of pollution in the watershed [42]. Among the different heavy metals, Cd shows a higher level of concentration which did not support any life or for drinking purposes (3 μg L−1) [43]. Cd is the typical anthropogenic metal affected by human activities [44] and showed enrichment. It is shown that Cd is associated to a greater extent with colloidal materials in surface runoff which can easily be transported into river flow [45]. Metals, such as Cu, Zn, and Pb, have a high affinity to human substances present in organic matter. The presence and quality of organic matter differentially influence the binding of metals within the sediments, reducing the adsorption of Cd and Co and increasing the adsorption of Zn [46]. Discharge of industrial, sewage, and poultry waste largely untreated forms may cause the elevation of metals in the water [47–49]. The water quality shows poor quality at those sites which drain sewage of the twin cities, while at downstream sites, the natural process shows some recovery from stress conditions due to the huge amount of sewage waste from the urban [50]. Activities of humans can change the smallest change in the ecosystem, especially downstream of the Soan River. The poor quality of water at downstream rather than upstream stations can result from several human activities, sewage, nutrient, sedimentation, and agriculture pesticides residue run-off. Wahizatul et al. [51] also studied in the Sekayu stream and found that agricultural and recreational activities were directly related to the destruction of aquatic species diversity in the Sekayu recreational forest. The higher organism abundance at site A is related to greater availability of coverage of riparian vegetation, which offers them a great supply of hiding places, allochthonous material, and food availability. Roque et al. [52] pointed out that the area with greater vegetation coverage has greater taxonomic richness. Although, at sites C and D, low diversity is found which could be related to the loss of riverbank vegetation and replaced by waste material, shrubby, exotic vegetation, and a lower quantity of heterogeneous substrate. This phenomenon was noted by [53]. Adamu Mustapha and Geidam [54] reported that high nutrients loading at urban sites are due to discharge of sewage wastewater of Rawalpindi and Islamabad.

Chironomidae (Diptera) were most abundant at downstream of the Soan River. They show no variation and are found in all stations. Yule and Sen [32] reported that in Malysia, Chironomidae is probably the most abundant and diverse group of all macroinvertebrate's streams. The sandy or muddy areas and slow-flowing or standing streams with a high number of sediment particles are the best areas where Chironomidae can excel [32, 55]. Due to heavy rainfall, the flood affected the macroinvertebrates from all the sites. Thus, effect seasonal taxa richness. The member of Chironomidae was most affected by the flood. The mayflies (Ephemeroptera) and true bug (Hemiptera) did not show any response to heavy rainfall because they are morphologically better adapted, attachment abilities to stones, mobility in water and behavioral pattern during mating. Holomuzki and Biggs [56] studied the behavioral pattern in response to the flood. The fluctuation of water level in the winter season remained very low. This is the major stressing factor for littoral organisms. Nairn et al. and Gopal [57, 58] also recorded a similar finding on littoral destruction. The macroinvertebrate density in the Soan River was found to be the lowest when the monsoon season starts and increases when the monsoon stops. Wallace et al. and Jakob et al. [59, 60] pointed out that monsoon floods decrease macroinvertebrates' density, especially Chironomid species known as two-winged flies. EPT was not found abundantly in any collection points, especially downstream. EPT members are known to be the most sensitive insects to environmental stress. Therefore, the presence of EPT upstream indicates a relatively clean environment [61, 62]. Therefore, the EPT can be used for potential bioindicator purposes. The BMWP index shows poor results for all the sampling sites, but some sites show fair biological quality at site A as well as ASPT [62]. Therefore, the presence and absence of macroinvertebrates along with water physicochemical analysis at upstream and downstream shows the influence of anthropogenic and natural influences. This suggests that aquatic insects can be used to access the water management in Pakistan as the role of potential bio-indicators.
