Holistic Modeling to Design Basin-Wide Offsets

Holistic Modeling to Design Basin-wide Offsets

The 100 MW Gulpur Hydropower Project(GHPP) isa Run-of-River facility being built on the Poonch Riverin the Himalayan foothills in the Pakistan Administered Kashmir (PAK).The river itself is a national park, established primarily to protect the endangered Mahaseer fish (Tor putitora), and harbors a population of the Critically Endangered Kashmir Catfish (Glyptothorax kashmirensis), along with 35 other fish species.The project was designed to conform to the policies of the IFC and ADB, the two principle lendersto the project.Located in a Critical Habitatthe project was required to achieve ‘net gain in biodiversity’.The local wildlife legislationalso required the project to achieve ‘betterment of the national park’.The Gulpur Hydropower Project presents a unique example of a design that aims to achieve offsets on a basin-wide scale through a combination of technical and institutional mechanisms.Given a high level of environmental sensitivity, state-of-the art environmental flow modeling tools and techniques were used to demonstrate the credibility of the environmental design.DRIFT (Downstream Response to Imposed Flow Transformation), a holistic environmental flow assessment model used extensively in Southeast Asia and Africa, and previously tested on similar rivers in Pakistan was applied to study the basin level impact of various flow and biodiversity management scenarios.

Figure A:Project Setting

The map in Figure Aillustrates the general setting of the project. The Poonch River originates in the western foothills of the Pir Panjal Range. The river is narrow and descends steeply until it reaches the foothill areas where the gradient flattens out and the river widens as it is joined by several tributaries. The river flows into the Mangla Lake that is the reservoir of Mangla Dam, situated at the confluence of the Poonch and Jhelum Rivers. Flows in the Poonch River are highest in the summer months driven first by snow melt and then by the monsoon rains. Summer water temperatures in the lower Poonch approach 30ºC.

The project was originally conceived in 2004 as part of a hydropower resource assessmentwhich proposed a cascade of four hydropower projects over the 100 km length of the river in PAK. Meanwhile, environmental studies conducted on the river by an independent organization, the Himalayan Wildlife Foundation (HWF), indicated the presence of rich aquatic biodiversity including Endangered, Vulnerable, Near Threatened and endemic fish species, as well as the Near Threatened Eurasian Otter.Recognizing the ecological importance of the river, the authorities notified the river as a national park. These developments changed the entire investment perspective for the project, and the very viability of the project became questionable.At this point, HWF approached Mira Power, the project owner with the proposition that a win-win scenario could be explored, provided commitments could be made by the project owner and the government to finance the protection of the national park.The rationale behind the proposition was that the national park had no future given the very limited financial resources available with the government for management.Significant threats to biodiversity included illegal fishing using nets as well as explosives, and extensive mining of sand and gravel from the river bed.

The river consists of a series of stretches of pools, riffles, and rapids, providing habitats to fish of concern over the entire stretch of the river.The important breeding areas of the Endangered Mahaseer and of some other fish of conservation importance, however, are mainly confined to the segment upstream of the proposed dam.Management of fish populations downstream of the dam was therefore a special concern in the environmental assessment of the project.

Selection of Model for Environmental Flow Assessment

To build on this proposition suggested by HWF and to demonstrate its feasibility presented a special analytical challenge.In addition to environmental flow (EFlow) modeling to account for impact of barrier and flow related changes in the river, a prediction of impact of non-flow interventions such as protection of the river and management of sand and gravel mining from the river bed was required. The project owner engaged a team[1]to prepare an ESIA and undertake EFlow modelling.The DRIFT model was selected for EFlow assessment of the GHPP as:

It is a holistic interactive method, which provides the biophysical consequences for the downstream river for various scenarios of flow change.

It is based on Response Curves constructed from any relevant knowledge including expert opinion and local wisdom and as such is suitable for use in regions where there are few biophysical data available for the flow–related aspects of the rivers, as was the case for the Poonch River.

Selection of Assessment Sites

Given the design of the project which included a diversion dam and a power generation tunnel across a ridge that would drain downstream at a lower elevation, the followingrepresentative sites were selected to study the impacts on a basin-wide level.The sites were selected on the basis of a catchment delineation exercise specifically considering the biological and geomorphological aspects, and social uses of the river.

An upstream site (EF Site 1) that will not be affected, but the river ecosystem at this point will be affected by the barrier created by the dam.

A site downstream of the dam but upstream of the tailrace (EF Site 2) that will be affected by a decrease in river flow as a result of the upstream diversion of water into the power house tunnel.

A site downstream of the tailrace (EF Site 3) to predict any anticipated recovery of the river ecosystem from the peaking flow releases from the tunnel.

A range of hydrological indicators and biophysical indicators that respond to flow changes were chosen to study the impacts on the ecosystem at each selected site.In addition to hydrology, indicators were selected for hydraulics, geomorphology, water quality, riparian vegetation, algae, macroinvertebrates, fish, and river dependent wildlife such as otters and birds. Six species of fish were selected as indicators taking into account the conservation status, family, and social value inclusive of food and recreational importance.The non-flow or management indicators included fishing pressures, pressure from mining for sand, gravel and boulders, and water quality as affected by the human settlements in the basin.The Poonch River’s present ecological state (PES) was categorized on the basis of modification from the natural, with the natural condition seen as the reference condition.All the selected hydrological and biophysical indicators were categorized by the discipline experts as pristine (A), slightly modified (B), moderately modified (C), largely modified (D), seriously modified (E), and Critically/extremely modified (F).

Flow scenarios were set to simulate varying levels of minimum dry season release from the dam.The discrete levels studied were 4, 6, 8, 12, and 16 m3/s.The minimum five day mean flow of about 14 m3/s was an ecological consideration in setting the flow range for the maximum release, while minimum release above 20 m3/s would make the project economically unviable and would result in a power tariff unacceptable to the electricity regulator.The minimum releases in each scenario were constant releases through the year.

Scenarios Simulated

The management scenarios simulated consisted of, in addition to aNo Dam scenario,ABusiness as Usual (BAU)or Poor Protectionscenario where, based on a literature review of long term regional trends in fish richness and abundance in absence of protection and with anthropogenic pressures, fish populations over a 50 year period would be expected to reach a fraction of present day.

Protection Level 1 or Moderate Protection under which 2013 levels of non–flow–related pressures on the river are maintained. This scenario assumed limited resources and intermittent availability of funds that the government is presently investing with assistance from the Himalayan Wildlife Foundation. Experience from the past five years from this level of protection indicated that the fish richness and abundance remained practically stagnant.

Protection Level 2 or Enhanced Protection under which non–flow–related pressures would be reduced by 50% over time. The increase in fish abundance under this scenario would be of the order of 50%over a 50 year period. The protection measures and the human and financial resources required to achieve this level of protection formed the basis of the Biodiversity Action Plan (BAP) prepared for the project.

A Peaking Scenario where the plant was operated in a peaking mode where the turbines are shut down for an extended period in a day to store water in the dam, and then released through the turbines to generate power in the peak power demand period in the evening.

Impacts on Indicator Fish Species

Figure C summarizes the impacts on the indicator fish species under the scenarios evaluated. The indicator fish species include an Endangered (Mahaseer) and a Critically Endangered (Kashmir Catfish) species. The impacts on these two species are indicative of the range of impacts on other species present in the river.

Impacts on Endangered Mahaseer Fish

With no dam in place, at all EFflow Sites upstream and downstream of the dam the population of Mahaseer was predicted to decline by about 95% in the next 52 years under BAU Scenario. It was predicted to decline by about 58% under Moderate Protection scenario, and improve by about 50% under Enhanced Protection scenario. The results show that a meaningful and effective protection system is essential for recovery of this species in the river. At EF Site 1 with dam in place, the population of Mahaseer was predicted to decline by about 80% with Poor Protection under BAU scenario. With Enhanced Protection, the population was predicted to improve by about 80%. The dam will benefit the population of Mahaseer at EF Site 1 upstream of the dam, mainly because the two importantbreeding tributaries for this fish are located upstream of the dam. The impact of the barrier effect of the dam upstream of the dam, however, will be small in comparison to the impact of protection measures or lack thereof.

At EF Site 2 with dam in place, Mahaseer will practically be eliminated under the BAU scenario. Assuming Enhanced Protection, a minimum release of 4 m3/s from the dam was predicted to improve the conditions only marginally, with 7% of the fish surviving (decline of 93%), while a release of 8m3/s will improve the survival to 9% (91% decline). However, an increase to16 m3/s from the dam could improve the survival to 59% (decline of 41%).

Figure C: Impact on Indicator Fish Species under Scenarios Studied

Blue and green are major changes that represent a move towards natural: green = 40-70%; blue = >70%. Orange and red are major changes that represent a move away natural: orange = 40-70%; red = >70%. Baseline, by definition, equals 100%.

Scenario Nomenclature: ND=No Dam, Pro1=Moderate Protection, Pro2=Enhanced Protection, GX is minimum release from Gulpur dam, where X stands for flow in m3/s

NDPro 1 / NDBAU / NDPro 2 / G8PeakBAU / G4ORBAU / G4ORPro 2 / G6ORBAU / G6ORPro 2 / G8ORBAU / G8ORPro 2 / G12ORBAU / G12ORPro 2 / G16ORBAU / G16ORPro 2
Mahaseer
EF Site 1 / –60 / –96 / 47 / –80 / 80 / –80 / 80 / –80 / 80
EF Site 2 / -55 / -92 / 51 / -100 / -93 / -100 / -91 / -100 / -87 / -100 / -61 / -100 / -42
EF Site 3 / -59 / -94 / 51 / -100 / -100 / -8 / -100 / -8 / -100 / -8 / -100 / -8 / -100 / -8
Pakistan Labeo
EF Site 1 / –64 / –86 / 62 / –79 / 69 / –79 / 69 / –79 / 69
EF Site 2 / -59 / -77 / 58 / -100 / -26 / -99 / -5 / -99 / -2 / -99 / 5 / -98 / 11
EF Site 3 / -59 / -87 / 60 / -100 / -89 / 61 / -89 / 61 / -89 / 61 / -89 / 61 / -89 / 61
Kashmir Catfish
EF Site 1 / –3 / –62 / 31 / –80 / 21 / –80 / 21 / –80 / 21
EF Site 2 / -8 / -62 / 15 / -100 / -91 / -100 / -89 / -100 / -86 / -100 / -71 / -98 / -45
EF Site 3 / -8 / -62 / 20 / -100 / -46 / 57 / -46 / 57 / -46 / 57 / -46 / 57 / -46 / 57
Twin–Banded Loach
EF Site 1 / 4 / –64 / 34 / 23 / –83 / 23 / –83 / –83 / 23
EF Site 2 / -1 / -54 / 47 / -100 / -90 / -100 / -83 / -100 / -78 / -99 / -50 / -91 / -14
EF Site 3 / -1 / -53 / 48 / -100 / -7 / 89 / -7 / 89 / -7 / 89 / -7 / 89 / -6.9 / 89
Garua Bachwaa
EF Site 1 / -66 / –99 / 73 / 8 / –100 / 8 / –100 / –100 / 8
EF Site 2 / -60 / -94 / 86 / -95 / -89 / -95 / -89 / -95 / -88 / -95 / -53 / -95 / -9
EF Site 3 / -60 / -96 / 80 / -100 / -99 / 64 / -99 / 64 / -99 / 64 / -99 / 64 / -99 / 64
Snow Trout
EF Site 1 / –24 / –40 / 19 / 29 / –25 / 29 / –25 / –25 / 29

At EF Site 3 with dam in place, Mahaseer will again practically be eliminated under the Poor Protection or BAU scenario. The principle reason for this is that in addition to impact of Poor Protection, the main breeding areas of Mahaseer are located upstream of the dam.With Enhanced Protection, the decline of Mahaseer will be restricted to 8% of present day. Additional mitigation measures such as stocking of Mahaseer from the hatchery were proposed as a mitigation to maintain the population of Mahaseer to at least present day levels.

Impacts on Critically Endangered Kashmir Catfish

With no dam in place, Kashmir Catfish population was predicted to decrease by around 60% under BAU scenario. However, the population was predicted to increase by about 20% under Enhanced Protection scenario.

At EF Site 1 with dam in place, the population was predicted to decrease by around 80% under BAU scenario. However, under Enhanced Protection, the fish population was predicted to increase by about 21%. This fish does not benefit from Enhanced Protection as much as the Mahaseer as it is not a target of subsistence or recreational fishing, and can take refuge in the crevices in the boulders where it is less likely to be captured by netting.

At EF Site 2 with dam in place, Kashmir Catfish fish will practically be eliminated under the BAU scenario. Under the Enhanced Protection Scenario, a minimum release of 4 m3/s from the dam was predicted to improve the conditions only marginally, with 9% of the fish surviving (91% decline), while a release of 8 m3/s will improve the survival to 14% (86% decline). However, an increase of minimum release to 16 m3/s from the dam could improve the survival of fish to 55% (decline of 45%). Being smaller in size, this fish benefits more from low flows due to increase in habitat availability. It also benefits from absence of bigger predators such as Mahaseer.

At EF Site 3 with dam in place, the decline in fish population was predicted to be 46% with Poor Protection under the BAU scenario. This affect is relatively lower in comparison to that on the Mahaseer because at EF Site 3 the fish benefits from the lower predation associated with decline in population of Mahaseer. Under Enhanced Protection Scenario, the fish population is expected to rise by 57% which is a significant increase. The fish will be eliminated under the Peaking Scenario due to instability in the flows and daily reduction in habitat.

Ecological Integrity of the River

The rivers present ecological state (PES) was categorized on the basis of modification from the natural, with the natural condition seen as the reference condition.Categories defined for individual indicators and for the river as a whole consisted of pristine (A), slightly modified (B), moderately modified (C), largely modified (D), seriously modified (E), and Critically/extremely modified (F). With Poor Protection or Business as Usual, the ecosystem integrity of the river which is presently Mid Category C was predicted to deteriorate to a Low Category D over the next 52 years at all EF Sites. With Enhanced Protection and with dam in place, the ecological integrity of the river upstream of the dam and downstream of the tailrace was predicted to improve from present Mid Category C to borderline Category B/ Category C. At EF Site 2 which represents the 0.7 km low flow section, the ecological integrity of the river was predicted to deteriorate to mid Category D, which would still be better than those under the no-dam Business as Usual case.

Conclusions

To compare the economic impact and ecological benefit expected by increasing the minimum environmental flow, loss in power generation was estimated for varying levels of EFlows and compared with decline in populations of Mahaseer and Kashmir Catfish in view of their conservation importance. This analysis was conducted for the 700m low flow section downstream of the dam only, as the population of the fish and integrity of the ecosystem will improve overall both upstream of the dam and downstream dam after implementation of Enhanced Protection.The results showed that when minimum flow is increased from 4 m3/s to 8 m3/s, the benefit to Mahaseer and Kashmir Catfish is not significant. However, when the minimum flow is increased from 8 m3/s to 16 m3/s, a noticeable benefit to their survival in the low flow segment is predicted. The financial impacts however increase on a linear scale as the EFlow is increased. Loss in power generation was estimated at 4.0%, 7.8%, and 14.8%, for EFlows of 4, 8 and 16 m3/s respectively. Since only a small segment of the river 700 m in length is impacted and the Project aims to achieve net gain in biodiversity through the length of Poonch River in PAK through implementation of the BAP, an EFlow of 4 m3/s for the Project where the financial return of the project is not severely impacted was agreed upon with the concerned stakeholders, the wildlife department, and the environmental regulator.

The Biodiversity Action Plan was formulated to address regional biodiversity concerns and to achieve net gain under IFC’s Performance Standard 6 and Safeguards Requirement (SR) 1 of ADB’s SPS. It addresses the implementation of the Enhanced Protection scenario to restore the biological resources of the Poonch River Basin. The government and the owner have signed an agreed to implement the BAP.The BAP strategy consists of:

Putting in place a protection system for the national park partly financed by the project and implemented by an Independent Organization

Active support from the wildlife department by providing staff for protection and assistance in coordination with other government line departments such as police, district administration, and mining department

Oversight and monitoring by the Wildlife Management Board

Construction and operation of a Mahaseer fish hatchery for stocking of fish downstream of the powerhouse

A sediment mining plan to manage community mining of sand and gravel from the river while protecting important fish habitat

Monitoring and evaluation of effectiveness of BAP by an Independent Third Party on a long term basis

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[1]Hagler Bailly Pakistan conducted the ESIA and Southern Waters supported HBP in EFlow assessment using DRIFT model