Ecology of Binwa a Western Himalayan Hill Stream in relation to Water Quality

Binwa is a perennial hill stream of the Western Himalayan region of Himachal Pradesh. During the present investigation, four observation sites based on altitudinal differences were selected, i.e., Kharli(S1), Baijnath (S2), near Chobin (S3), and Triveni (S4) and water samples were analyzed for physico-chemical and biological parameters for one year (Mar.2011-Feb.2012). Water temperature, water current, dissolved oxygen, turbidity, T.D.S., electric conductivity, total Hardness, phosphate, and nitrate had played an essential role in determining the variations in planktonic and macroinvertebrate fauna of the stream.Species diversity indices such as Simpson, Shannon and Wiener, and Margalef’s diversity index of macroinvertebrates were worked out for all the observation sites. Based on the comparison of physico-chemical parameters of water samples with different standards prescribed for drinking water, water quality index for four stations calculated. Similarly, EPT taxa (Ephemeroptera, Plecoptera, Trichoptera) measured, and EPT index computed. The water quality of the stream deteriorates downstream from head to mouth due to different types of anthropogenic interferences. The findings revealed that stream has no pollution at S1, while it is oligotrophic from S2 to S3 and meso-oligotrophic at S4. Current World Environment www.cwejournal.org ISSN: 0973-4929, Vol. 15, No. (2) 2020, Pg. 186-193


Introduction
A stream is a watercourse of all sizes having a specific course, in which minerals and nutrients (inorganic and organic matter) are essential parts, flow along the longitudinal gradient from the head to mouth. Streams located in the Western Himalaya play a significant role ecologically (vast biodiversity), economically (hydroelectric and fishery potential), and socially (sacred religiously to adjoining inhabitants). Hill streams have some unique features such as swift water current, heterogeneous substratum, high dissolved oxygen, and low nutrient, and have unique biodiversity, which is intolerant to pollution. Binwa stream which is selected for the study has two religious places on its left bank, visited by thousands of people; stream is sacred to Gaddi people (a tribal community) living in its vicinity and also an important breeding ground of Tor sp. (Mahaseer fish) from Beas river (Sharma,1 ). By determining the water quality of the stream, one can assess the stream's health as well as its suitability for drinking. This is the reason that during the investigation, water samples were analyzed for hydrobiological (physio-chemical, phytoplankton, zooplankton) and macroinvertebrates of the stream. Water quality is determined by using water quality index (W.Q.I.) on different physico-chemical parameters and their comparison with the standard prescribed by different organizations such as ICMR, 2 BIS, 3 CPCB, and WHO, 4 . Macroinvertebrates were used to determine the species diversity at different observation sites, while the taxa belonging to Ephemeroptera, Plecoptera, and Trichoptera were used to determine the EPT index. A checklist of macroinvertebrates has been also given.

Study Area
During the present study, four observation sites selected for collection of water samples and macroinvertebrates, i.e., Kharli as S 1 , (2822 m above msl), Baijnath as S 2 , (945 m above msl), near Chobin as S 3 , (746 m above msl) and Triveni as S 4 , (572 m above msl)on Binwa, a Western Himalayan perennial hill stream, located in district Kangra, Himachal Pradesh. It originates from the southern slopes of the Dhauladhar range of Mid Himalaya and has confluence with Beas river at Triveni, after covering a distance of 48 Km from head to mouth. Along its course, it supports a vast human population of the Baijnath block ofKangra district for drinking and irrigation facilities. However, in this relatively short distance, it experiences an impressive fall of about 3100 m (3678 m elevation at its head and 539 m at its mouth). The primary habitat is comprised of runs and riffles with some pools and a substrate of boulders and cobbles. Drainage network in the study area, all the streams/Nullah have been ordered as per Strahler, 5 and Rosgen, 6 . A stream is categorized as B3-type. . For the plankton study, 100 litters of water were filtered through the plankton net made up of bolting silk No. 25 (0.3 mm mesh) and fitted with a wide-mouthed bottle. Planktons were preserved in 4% formaldehyde solution. Macroinvertebrates were collected in the Surber sampler net by making a disturbance in the substratum of the stream, unsettling them, and then collected in the bucket and at last preservation in 4% formaldehyde solution. The density of these macroinvertebrates mentioned as an individual per square meter. The books consulted for the identification of the plankton and benthos were: (Pennak,8 ;Merritt & Cummins,9 ; Thorp and Covich, 10 and Subramanian and Sivaramakrishnan, 11 ). Counting of plankton was done with the help of the Sedgwick-Rafter cell counter (Wetzel and Likens, 12 ). Species diversity was calculated using diversity indices (Shannon and Wiener, 13 ;Simpson,14 ). Since there is no industrial development occurred around the stream, and also there is not much change in other conditions (anthropogenic disturbances). So the findings will be useful in determining the water quality for various uses and maintaining the biodiversity of the stream. Water quality index has been calculated for nine physico-chemical parameters of a water sample by consulting the Jindal and Sharma, 15 and Batabyal& Chakraborty, 16 Water Quality Index (WQI) = qi.wi  (Table-1). Water temperature was maximum during summer (May and June), minimum during winter throughout the stream, and increased water temperature in summer increase the respiratory rate, decrease oxygen holding capacity so as elevate the free CO 2 in the system; water velocity observed maximum in monsoon (July and August) due high rate of precipitation throughout the course (S 1 -S 4 ), at S 2 water velocity is high this might be due to great fall in a gradient from S 1 to S 2 , while slightly high water current at S 1 during pre-summer (April) and summer (May and June) have been observed, which might be due to melting of a glacier in the catchment area. High water current during monsoon posed a threat of wash away to planktons and aquatic insect larvae and showed an inverse relation with them. While T.D.S., turbidity, chlorides, and nutrients such as nitrates and phosphates showed their maxima during the monsoon period, and are in direct relation with water current. The rise of these parameters during monsoon might be due to loose and fragile catchment downstream, agricultural runoff from catchment area, sewage at S 2 and dumping of solid waste at different places into the stream. Dissolved oxygen was maximum during winter and minimum in summer, as water has high oxygen holding capacity at low temperature (Malik and Bharti, 17 , Jindal and Singh, 18 ).

Simpson's Biodiversity Index
Bacillariophyceae, Chrysophyceae and aquatic insects (EPT taxa) showed positive correlation with dissolved oxygen at all the observation sites (Jabeen and Barbhuiya, 19 ). While Chlorophyceae, Cynophyceae, Euglenophyceae, and Protozoa showed an inverse relation with dissolved oxygen, and direct relation with T.D.S., electric conductivity, nitrate, and phosphates. Chrysophyceae showed complete absence from S 4 (Triveni), which might be due to low dissolved oxygen and high nutrient load. In contrast, Euglenophyceae reported only from S 3 and S 4 and utterly absent at S 1 and S 2 , might be due to shallow water temperature. Insect larvae belonging to order Ephemeroptera, Plecoptera and Trichoptera are used to monitor the water quality, while different diversity indices used to study the species richness and evenness of species composition in the stream to overall access the health of the stream. Role of Baetidae as bioindicator has been used to monitor the rivers health in western ghats (Kubendran et al.,22 ).
EPT index values showed that water quality at S 1 is of 'Excellent,' while on remaining stations, it is reasonably suitable for human consumption (

Conclusion
Chrysophyceae and plecopteran naiads are predominantly the pollution intolerant (observed upstream) and perished in polluted waters, while euglenoids, blue-green algae, and dipterans observed in polluted waters. The results of the water quality idex and EPT index revealed that water quality deteriorates down the stream due to anthropogenic interferences such as entry of domestic sewage, agricultural runoff, mining, dumping of solid waste, and tourist activities in the stream habitat. While species diversity indices of macroinvertebrates showed that in the middle section (S 2 and S 3 ) of stream moderate water current, high dissolved oxygen, nutrients, allochthonous addition, and, more importantly, the heterogeneity in habitat and substratum contribute to high biodiversity. Since there is no industrial establishments happened in and around the vicinity and no study are conducted on hydrobiology of the stream, so the findings will be of immense use for biodiversity conservation, maintaining fish breeding grounds and monitoring the water quality of Binwa.