Editing Small hydro (section)

== Environmental Impacts ==
Environmental effects of small hydro projects are understudied; impacts are dependent upon individual project design. Changes in the hydrologic cycles of an area can result in loss of river cohesion and connectivity, contributing to habitat degradation and loss of biodiversity for fish and macroinvertebrates.<ref>{{Cite journal |last=Feio |first=Maria João |last2=Hughes |first2=Robert M. |last3=Serra |first3=Sónia R. Q. |last4=Nichols |first4=Susan J. |last5=Kefford |first5=Ben J. |last6=Lintermans |first6=Mark |last7=Robinson |first7=Wayne |last8=Odume |first8=Oghenekaro N. |last9=Callisto |first9=Marcos |last10=Macedo |first10=Diego R. |last11=Harding |first11=Jon S. |last12=Yates |first12=Adam G. |last13=Monk |first13=Wendy |last14=Nakamura |first14=Keigo |last15=Mori |first15=Terutaka |date=2023 |title=Fish and macroinvertebrate assemblages reveal extensive degradation of the world's rivers |url=https://onlinelibrary.wiley.com/doi/10.1111/gcb.16439 |journal=Global Change Biology |language=en |volume=29 |issue=2 |pages=355–374 |doi=10.1111/gcb.16439 |issn=1365-2486 |pmc=10091732 |pmid=36131677}}</ref> Small dams and ensuing water diversion may hinder the movement of fish as well and contribute to methane emissions from decomposed biomass.<ref>{{Cite journal |last=Anderson |first=Elizabeth P. |last2=Freeman |first2=Mary C. |last3=Pringle |first3=Catherine M. |date=2006 |title=Ecological consequences of hydropower development in Central America: impacts of small dams and water diversion on neotropical stream fish assemblages |url=https://onlinelibrary.wiley.com/doi/10.1002/rra.899 |journal=River Research and Applications |language=en |volume=22 |issue=4 |pages=397–411 |doi=10.1002/rra.899 |issn=1535-1467|url-access=subscription }}</ref><ref>{{Cite journal |last=Nautiyal |first=Himanshu |last2=Goel |first2=Varun |date=2020-08-20 |title=Sustainability assessment of hydropower projects |url=https://linkinghub.elsevier.com/retrieve/pii/S095965262031708X |journal=Journal of Cleaner Production |volume=265 |pages=121661 |doi=10.1016/j.jclepro.2020.121661 |issn=0959-6526|url-access=subscription }}</ref>

Multiple small hydropower projects are occasionally placed segmentally on rivers, but little research has been done on the effects of multiple installations in a collective area. In India, cumulative effects of multiple SHP projects are not considered prior to granting hydropower developments.<ref>{{Cite journal |last=Erlewein |first=Alexander |date=2013-11-01 |title=Disappearing rivers — The limits of environmental assessment for hydropower in India |url=https://linkinghub.elsevier.com/retrieve/pii/S0195925513000760 |journal=Environmental Impact Assessment Review |volume=43 |pages=135–143 |doi=10.1016/j.eiar.2013.07.002 |issn=0195-9255|url-access=subscription }}</ref> In China, researchers found the effects of river connectivity on a river with 31 small hydro projects to significantly outweigh the impacts associated with a river containing 4 larger-scale projects.<ref>{{Cite journal |last=Kibler |first=Kelly M. |last2=Tullos |first2=Desiree D. |date=2013 |title=Cumulative biophysical impact of small and large hydropower development in Nu River, China |url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/wrcr.20243 |journal=Water Resources Research |language=en |volume=49 |issue=6 |pages=3104–3118 |doi=10.1002/wrcr.20243 |issn=1944-7973}}</ref> 

Previous studies on the sustainability of hydropower focus on greenhouse gas emission estimations, which are generally lesser than other conventional or renewable energy systems. Assessments of sustainability often do not consider additional parameters, such as environmental impacts, land use, social costs and cultural effects.<ref>{{Cite journal |last=Nautiyal |first=Himanshu |last2=Goel |first2=Varun |date=2020-08-20 |title=Sustainability assessment of hydropower projects |url=https://linkinghub.elsevier.com/retrieve/pii/S095965262031708X |journal=Journal of Cleaner Production |volume=265 |pages=121661 |doi=10.1016/j.jclepro.2020.121661 |issn=0959-6526|url-access=subscription }}</ref> With climate change threatening the reliability of seasonal river flows, the efficiency and sustainability of small hydro for energy generation is unknown.<ref>{{Cite journal |last=UNIDO |last2=Power |first2=International Center on Small Hydro |date=2022 |title=World Small Hydropower Development Report 2022 |url=https://digitallibrary.un.org/record/4025088?v=pdf |journal=Global overview / United Nations Industrial Development Organization |language=en}}</ref>