Key to Bhutan’s economic development strategy is the expansion of the country’s hydropower projects, which requires the construction of a number of large dams. As dams affect the natural hydrological regime of rivers, the objective of this study was to assess these impacts on water quality and macroinvertebrate communities. Baseline physical and chemical properties of rivers in central Bhutan were gathered to provide spatial context for hydrological change associated with hydropower development. Physico-chemical measures from central Bhutan rivers suggested that aquatic macroinvertebrate communities are not currently impacted1 by poor water quality. An in situ experiment using flow diversion barriers in Chamkharchu at Jakar (Bumthang) was conducted to assess the short-term impacts of reduced water velocity on benthic macroinvertebrate communities to simulate the impacts of flow velocity changes associated with reaches downstream of hydropower facilities. We found benthic macroinvertebrate taxa
abundance, richness and diversity were not significantly different between high and low flow velocity treatments, but community composition was significantly different between before and after the construction of flow diversion barriers, with reduced abundance of rheophilic (flow-dependent) taxa in treatments with reduced velocity. Current impacts of hydropower facilities are focused on the construction phase. This study has highlighted that the operation of hydropower facilities can also impact the ecological condition of rivers, and that these long-term impacts must be included in the decision making processes for hydropower development. Further investigation is warranted to determine how wide-ranging these impacts will be throughout Bhutan.
Key Words :
Rheophilic macroinvertebrates, river regulation, flow regime, impoundment, Chamkharchu, Bhutan
Allan, C., R. J. Watts, S. Commens, and D. S. Ryder. 2009. Using adaptive management to meet multiple goals for flows along the Mitta Mitta River in south-eastern Australia. Pp. 59-71 in Allan, C and G.H. Stankey, Editors. Adaptive Environmental Management. Springer, Netherlands.
Aquastat: Food and Agriculture Organisation of the United Nations (FAO). 2011. Bhutan. Available from ://www.fao.org/nr/water/aquastat/countries_regions/btn/BTN-‐CP_eng.pdf (8th June 2015).
Bednarek, A. T. 2001 Undamming rivers: A review of the ecological impacts of dam removal. Environmental Management 27:803-14.
Beketov, M. A. 2008. Community structure of Ephemeroptera in Siberian streams. Entomological Science 11(3):289–299.
Beldring, S., and A. Voksø. 2011. Climate Change Impact on Flow Regimes of Rivers in Bhutan and Possible Consequences for Hydropower Development. Norwegian Water Resources and Energy Directorate, Norway.
Bhatt, J. P., A. Bhaskar, and M. K. Pandit. 2005. Biotic communities of Kishangangariver: A pre-impoundment case study of a Himalayan river. Aquatic Ecosystem Health & Management 8:259-265.Biggs, B. J., and S. Stokseth. 1996. Hydraulic habitat suitability for periphyton in rivers. Regulated Rivers: Research & Management 12(2):251-261.
Bookhagen, B., and D. W. Burbank. 2010. Toward a complete Himalayan hydrological budget: Spatiotemporal distribution of snowmelt and rainfall and their impact on river discharge. Journal of Geophysical Research: Earth Surface 115(F3).
Boulton, A., M, Brock, B, Robson, D. Ryder, J. Chambers, and J. Davis. 2014. Australian Freshwater Ecology: Processes and Management. John Wiley & Sons, London.
Brewin, P. A., and S. J. Ormerod. 1994. Macroinvertebrate drift in streams of the Nepalese Himalaya. Freshwater Biology 32(3):573-584.
Brewin, P. A., S. T Buckton, and S. J. Ormerod. 2000. The seasonal dynamics and persistence of stream macroinvertebrates in Nepal: do monsoon floods represent disturbance? Freshwater Biology 44(4):581-594.
Brooks, A.,J., B.,C. Chessman, and T. Haesler. 2011a. Macroinvertebrate traits distinguish unregulated rivers subject to water abstraction. Journal of North American Benthological Society 30:419-435.
Brooks, A.,J., M. Russell, R. Bevitt, and M. Dasey. 2011b. Constraints on the recovery of invertebrate assemblages in a regulated snowmelt river during a tributary-sources environmental flow regime. Marine and Freshwater Research 62:1407-1420.
Brunke, M., A. Hoffmann, and M.,Pusch. 2001. Use of mesohabitat-specific relationships between flow velocity and river discharge to assess invertebrate minimum flow requirements. Regulated Rivers: Research and Management 17:667-676.
Bunn, S. E., and A. H. Arthington. 2002 Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30:492-507.
Chhopel, G. K. 2014. Sustainability of Bhutan’s Hydropower. Hydro Nepal 14: 73-76.
Clarke, K. R., and R. M. Warwick. 2001. An approach to statistical analysis and interpretation. Change in Marine Communities. Natural Environment Research Council, Plymouth.
Collier, K. J. 1995. Environmental factors affecting the taxonomic composition of aquatic macroinvertebrate communities in lowland waterways of Northland, New Zealand. New Zealand Journal of Marine and Freshwater Research 29:453-465.
Cushman, R. M. 1985. Review of ecological effects of rapidly varying flows downstream from hydropower facilities. North American Journal of Fisheries Management 5:330-339.
De Jalon, D., D. Garcia, P. Sanchez, and J. A. Camargo. 1994. Downstream effects of a new hydropower impoundment on macrophyte, macroinvertebrate and fish communities. Regulated Rivers: Research & Management 9:253-261. Department of Hydro Met Services. Ministry of Economic Affairs. http://www.hydromet.gov.bt/ accessed 27th October 2015.
Dewson Z. S., A. B. W. James, and R. G. Death. 2007. A review of the consequences of decreased flow for instream habitat and macroinvertebrates. Journal of the North American Benthological Society 26:401-15.
Dubey, G. P. 1978. Survey of the waters of Bhutan: Physiography and fisheries potential. Available from http://www.fao.org/3/contents/5076d0e0‐d437-5b5d-880c‐6b0075c05f5/L8853E00. html. Retrieved June 8th 2015.
Durance, I., and S. J. Ormerod. 2009. Trends in water quality and discharge confound long‐term warming effects on river macroinvertebrates. Freshwater Biology 54:388-405.
Englund, G., and B. Malmqvist. 1996. Effects of flow regulation, habitat area and isolation on the macroinvertebrate fauna of rapids in north Swedish rivers. Regulated Rivers-Research and Management 12:433-446.
Fonseca, D. M., and D. D. Hart. 1996. Density-dependent dispersal of black fly neonates is mediated by flow. Oikos 75:49-58.
Gillespie, B. R., L. E. Brown, and P. Kay. In Press. Effects of impoundment on macroinvertebrate community assemblages in upland streams. River Research and Applications.
Giri, N., and O. P. Singh. 2012. Urban growth and water quality in Thimphu, Bhutan. Journal of Urban and Environmental Engineering 7:82-95.
Gooderham, J., and E. Tsyrlin. 2002. The Waterbug Book. A guide to the freshwater macroinvertebrates of temperate Australia. CSIRO publishing, Collingwood Australia.
Gross National Happiness Commission (GNHC). 2013. Eleventh Five-Year Plan Document: 2013-2018. Thimphu, Bhutan: Royal Government of Bhutan. Available from http://www.gnhc.gov.bt/
Growns I. O., and J. E. Growns. 2001. Ecological effects of flow regulation on macroinvertebrate and periphytic diatom assemblages in the Hawkesbury-Nepean River, Australia. Regulated Rivers: Research & Management 17:275-93.
Growns, I., I. Reinfelds, S. Williams, and G. Coade. 2009. Longitudinal effects of a water supply reservoir (Tallowa Dam) on downstream water quality, substrate a
riffle macroinvertebrate assemblages in the Shoalhaven River, Australia. Marine and Freshwater Research 60:594-606.
Hamerlík, L., and D. Jacobsen. 2012. Chironomid (Diptera) distribution and diversity in Tibetan streams with different glacial influence. Insect Conservation and Diversity, 5:319–326.
Hartmann, A., and O. Moog. 2008. Development of a field screening methodology to evaluate the ecological status of the streams in the HKH region. Pp. 17-24 in In O. Moog, D. Hering, S. Sharma, I. Stubauer and T. Korte, Editors. Proceedings of Scientific Conference on Rivers in the Hindu Kush Himalaya: Ecology and Environmental Assessment. Nepal.