49086-001: Upper Trishuli 1 Hydroelectric Power Project
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Environmental and Social Impact Assessment Final Report (Part 2) Project Number: 49086-001 June 2018 NEP: Upper Trishuli-1 Hydropower Project Prepared by Environmental Resources Management (ERM) for the Nepal Water & Energy Development Company Pvt. Ltd. And the Asian Development Bank. The environmental and social impact assessment report is a document of the borrower. The views expressed herein do not necessarily represent those of ADB's Board of Directors, Management, or staff, and may be preliminary in nature. In preparing any country program or strategy, financing any project, or by making any designation of or reference to a particular territory or geographic area in this document, the Asian Development Bank does not intend to make any judgments as to the legal or other status of any territory or area. Non-Technical Updated Environmental and Social Assessment Summary Report Chapter 6 Upper-Trishuli Hydroelectric Power Project Current Environmental and Social Baseline Conditions (Bajracharya et al. 2011) indicate climate change will affect flow regimes, as glaciers continue to decline in some parts of the region and monsoon patterns may become altered. Hydrographic data for the Project are based on a 44-year record of continuous daily observations made at Betrawati (Gauge Station 447, Nepal Department of Hydrology and Meteorology), located 14 kilometres downstream of the proposed UT-1 powerhouse (see Figure 6.1-8). To predict daily hydrographs at the UT-1 intake, Betrawati gauge data are adjusted downward by a factor of 0.8971 to account for the slightly smaller watershed area upstream of the gauge. The daily hydrographs show the extent of variation in daily discharge for representative low-flow and high-flow in years 1970 and 2000 respectively (see Figure 6.1-9). Source: ESSA 2014 Figure 6.1-8: Unimpaired Average Annual Discharge for the Trishuli River at the UT-1 Intake Dam 6.1-10 Non-Technical Updated Environmental and Social Assessment Summary Report Chapter 6 Upper-Trishuli Hydroelectric Power Project Current Environmental and Social Baseline Conditions Source: ESSA 2014 Figure 6.1-9: Daily Flow Hydrographs for Representative Low-Flow (1970) and High-Flow (2000) Years in Linear (Upper) and Logarithmic (Lower) Scales The Trishuli River carries a high sediment load, especially in the monsoon season, resulting from glacial melt, erosion, landslides and mass wasting. The riverbed material consists of boulders and cobbles, embedded in finer gravel, sand, and silt. 6.1.4. Groundwater Based on a hydrogeological study along the tunnel alignment, two types of aquifers were identified in the Project area: the surficial aquifer that supports local springs, and a deeper regional aquifer that exhibits an effective porosity of 40 percent and is hydrologically connected to the Trishuli River. There are about 45 springs within the Project footprint (Figure 6.1-10), of which about 16 springs (i.e. SP-4, SP-5, SP-6, SP-8, SP-9, SP-12, SP-13, SP-14, SP-16, SP-17, SP-25, SP-30, SP-34, SP-37, SP-42, and SP-43) are known to be sources of water supply for local communities (ESSA 2014). Some of these springs, however, were reported to have dried up after the 2015 earthquake and associated landslides. 6.1-11 Non-Technical Updated Environmental and Social Assessment Summary Report Chapter 6 Upper-Trishuli Hydroelectric Power Project Current Environmental and Social Baseline Conditions Data source: ESSA 2014, Figure source: ERM Figure 6.1-10: Springs in the Vicinity of the UT-I Project 6.1-12 Non-Technical Updated Environmental and Social Assessment Summary Report Chapter 6 Upper-Trishuli Hydroelectric Power Project Current Environmental and Social Baseline Conditions 6.1.5. Surface Water Quality 6.1.5.1. Baseline Water Quality Analysis A baseline water quality assessment was conducted at five locations (W-1 to W-5) in and around the Project site within the Trishuli River during 2011 as part of the EIA Study Report (NWEDC 2012), and also monthly from August 2013 to July 2014 at five different locations (F1 to F5) as part of the Supplemental ESIA study (ESSA 2014). These data are presented in Tables 6.1-4 through 6.1-7. Table 6.1-4: Water Quality Sampling Locations (2011) S.N. Sample No. Location River 1 W 1 Upstream of Confluence Bhote Koshi 2 W 2 Upstream of Confluence Trishuli 3 W 3 Downstream of Confluence Trishuli 4 W 4 Dam Site Trishuli 5 W 5 Confluence of Trishuli River and Ghatte Khola Ghatte Khola 6 W 6 Powerhouse Site (Mailun Dovan) Trishuli Source: NWEDC 2012 Table 6.1-5: Water Sampling Locations (August 2013 to July 2014) Site Latitude (N) Longitude (E) Location VDC Bank F1 28° 08' 41.4" 85° 18' 47.1" Upstream of dam site Syapru Left F2 28° 06' 47.8" 85° 16' 53.6" Diversion reach Dhunche Left F3 28° 05' 20.6" 85° 13' 50.4" Diversion reach Haku Right F4 28° 04' 50.1" 85° 13' 01.6" Diversion reach (Upstream Haku Right of powerhouse) F5 28° 04' 15.1" 85° 12' 29.0" Downstream of powerhouse Ramche Left Source: ESSA 2014 ° = degrees; ' = hours; " = minutes; E = east; N = north; VDC = Village Development Council Table 6.1-6: Water Quality Sampling Results (2011) Sampling Locations Parameters Unit NDWQS W 1 W 2 W 3 W 4 W 5 W6 Turbidity NTU 34 < 1 7.1 31 4 39 5(10) (Max) Conductivity ȝ6FP 127 63 115 120 53 112.7 1500 (Max) TDS PJ/ 55 27 50 52 23 49 1000 (Max) TSS PJ/ 116.6 2.6 88.9 42.8 14.8 133.8 - Total Solids PJ/ 38 149 109 48 194 183 Total Alkalinity PJ/DV&D&23 41 24 41 43 19 40 - Total Acidity PJ/ 86 103 77 77 120 206 - Chloride PJ/DV&O 2.5 1 2 5.6 1.5 NA 250 (Max) Nitrate PJ/DV123 0.8 1 1.3 1 < 0.1 0.7 50 (Max) Ammonia PJ/DV1 0.1 < 0.1 0.1 0 < 0.1 0.1 1.5 (Max) Total Hardness PJ/DV&D&23 55 28 51 51 16 48 500 (Max) Calcium PJ/DV&D 18 8 16 16 5 16 200 (Max) Source: NWEDC 2012 ȝ6FP = micro-Siemens per centimetre; CaCO3 FDOFLXPFDUERQDWH&O FKORULGHPJO PLOOLJUDPVSHUOLWUH1 QLWURJHQ NDWQS = Kathmandu Valley Drinking Water Quality Exceeds Values; NO3 = nitrate; NTU = nephelometric turbidity unit; TSS = total suspended solids 6.1-13 Non-Technical Updated Environmental and Social Assessment Summary Report Chapter 6 Upper-Trishuli Hydroelectric Power Project Current Environmental and Social Baseline Conditions Table 6.1-7: Water Quality Minimum and Maximum Values (August 2013 to July 2014) Parameters (units in mg/l F-1 F-2 F-3 F-4 F-5 NDWQS unless noted) Min Max Min Max Min Max Min Max Min Max pH 6.6 7.4 6.8 7.5 6.9 7.5 7 7.7 6.6 7.8 6.5-8.5 Electrical Conductivity, 1500 PKRVFP 91.4 150 85 161 81 150 81 151 86 150 Turbidity, (NTU) 1 200 5 175 1 175 4 480 1 225 5 (10 )* Total Suspended Solids 1 658 1.5 544 2 539 1 917 1.5 268 - Total Solids 90 1119 74 699 78 637 57 1243 68 553 - Settleable Solids 0.67 633.7 0.5 520.7 0.67 481 0.67 566 0.5 242.3 - Non-Settleable Solids 0.33 43 0.2 101 0.33 58 0.33 351 0.33 124 - Total Hardness as CaCO3 51 81 46 78 35 195.3 53 110 50 76 500 Total Alkalinity as CaCO3 39.6 68.8 40 62 35 61 40 236 40 107 - Sulphate 2.5 23.8 6.6 32 5.34 26.7 1.6 32.5 3.3 26.32 250 Chloride 1.9 4 1 5 0.5 4 1 5 0.97 5 250 Free Carbon Dioxide 0.58 2.3 1.1 2.33 0.58 2.33 0.56 2.9 0.58 2.33 - Ammoniacal - N BDL 0.33 BDL 0.1 BDL 0.25 BDL 0.14 BDL 0.8 - Nitrate - N 0.2 0.74 0.2 0.96 0.18 1.1 0.23 0.81 0.17 1.25 50 Nitrite - N BDL 0.03 BDL 0.03 BDL 0.07 BDL 0.03 BDL 0.01 - Fluoride BDL 0.29 BDL 0.23 BDL 0.32 BDL 0.28 BDL 0.33 0.5 (1.5) Biological Oxygen - Demand 1 5.5 0.7 5.5 0.5 9.4 0.5 7 0.5 3.6 Chemical Oxygen Demand 6 25 4 24 2 32 4 36 4 32 - Phenol BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL - Oil & Grease 1 6 1 5 1 4 1 4 2 6 Hydrogen Sulphide BDL 0.8 BDL 1.6 BDL 1.9 BDL 1.6 BDL 0.8 - Iron 0.18 9.4 0.17 7.9 0.18 7.8 0.23 6.9 0.23 6.8 0.3 (3.0) Manganese BDL 0.17 BDL 0.12 BDL 0.13 BDL 0.12 BDL 0.11 0.2 Cadmium BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 0.003 Lead BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 0.01 Copper BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 1.0 Nickel BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL - Silver BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL - Zinc BDL 0.05 BDL 0.08 BDL 0.04 BDL 0.04 BDL 0.05 3.0 Arsenic BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 0.05 Mercury BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 0.001 Source: ESSA 2014 *Values in parenthesis refer to the acceptable values only when an alternative is not available.