Staff Gauge Installation, Water Level Observation, Periodic Discharge Measurement, Sediment Sampling and Laboratory Analysis of Arun River for Upper Arun HEP and Ikhuwa Khola for Ikhuwa Khola HPP
Project: Upper Arun Hydroelectric Project and Ikhuwa Khola Hydropower Project
Assignment: Staff Gauge Installation, Water Level Observation, Periodic Discharge Measurement, Sediment Sampling and Laboratory Analysis of Arun River for Upper Arun HEP and Ikhuwa Khola for Ikhuwa Khola HPP
Location: Sankhuwasabha District, Nepal
Client: Soil Test (P) Ltd.
Duration: March 2018 to March 2020
Project Description: UAHEP is a Peaking Run of the River (PRoR) project with gated weir across the Arun River. Intakes on the left bank of the river are proposed to divert the design discharge of 78.8 m3/s through an intake tunnel to three underground desanding basins, a headrace tunnel of 7.8 km, surge tank, drop shaft, pressure tunnel, and ultimately to the underground powerhouse for power generation. UAHEP’s capacity is of 335 MW and annual energy generation of 2050 GWh.
Ikhuwa Khola Hydropower Project is located in Pawa Khola VDC of Sankhuwasabha District in Eastern Nepal. The installed capacity of the project is 30 MW. It has design discharge of 6.02 m3/s and net head of 601m. The headwork includes concrete gravity structure diversion weir of length 28m and maximum height of 6m. The desilting basin is of length 56m, width 8m and height 4m having two bays designed at 90% trap efficiency for 0.2mm size particles. The water is guided to the forebay (58m L X 10m B X 4m H) through inverted D-shaped Head Race Tunnel 2.5m X 2.5m. From the forebay water is guided to the surface powerhouse (35m L X 20m B X 28m H) through penstock of internal diameter 1.0 m to 1.4 m and thickness 12mm to 32mm. The powerhouse houses two vertical axis Pelton turbines and 2 synchronous 3-phase generators. Annual energy generation from the project is 181.74 GW-h which is evacuated in 132 kV, single circuit transmission line to nearest sub-station in Tumglingtar. The access road for the project is 8.1 km from the nearest road head to the powerhouse and 12.5 km from powerhouse to the headworks.
Scope of Services:
A. Gauge Installation:
1) Desk study and meeting with clients about the tentative location and schedule for the installation of manual gauges;
2) Gathering and transportation of all the necessary materials and equipment required for the installation;
3) Proper selection of the suitable location for the installation with reference to the coordinates/tentative location provided by the client;
4) Proper installation of manual gauges in single or more than 1 rock outcrop as feasible;
5) Gauge installation and water level observation in following locations:
• UAHEP Powerhouse- 4m (for 24 months)
• Chepuwa Khola- 3m (for 12 months i.e. December to May (6months) for 2 years)
• Leksuwa Khola- 3m (for 12 months i.e. December to May (6months) for 2 years)
• IKHPP Headworks-3m (for 12 months)
• IKHPP Powerhouse-4m (for 12 months)
6) Development of standard log book to record the gauge readings properly;
7) Provide training to the local staff gauge reader for taking reading as per DoED guidelines;
8) Preparation and submission of the manual gauge installation report and monthly water level observation data;
9) Equipment used:
• Graduated Aluminum gauge plate;
• Standard size Agrakh wood;
• Rock drilling equipment;
• Portable generator;
• Level pipe, plumb bell, hammer, bolts grips and accessories.
B. Discharge Measurement:
1) Desk study and meeting with clients about the tentative location, schedule and frequency for discharge measurement;
2) Gathering and transportation of all the necessary materials and equipment required for the measurement;
3) Proper selection of the suitable location for discharge measurement with reference to the coordinates/tentative location provided by the client;
4) Discharge Measurement in following locations:
• UAHEP Headworks- 8 times in 24 months duration by Sounding Reel Method using Bank Operated Cable Way;
• UAHEP powerhouse- 8 times in 24 months duration by Sounding Reel Method using the existing Suspension Bridge;
• Chepuwa Khola- 12 times in 24 months duration (i.e. December to May (6months) for 2 years) by Wading Rod Method;
• Leksuwa Khola- 12 times in 24 months duration (i.e. December to May (6months) for 2 years) by Wading Rod Method;
• IKHPP Headworks- 12 times in 12 months duration by Sounding Reel Method using Bank Operated Cable Way OR Wading Rod Method according to the flow condition; and
• IKHPP Powerhouse- 12 times in 12 months duration by Sounding Reel Method OR Wading Rod Method depending upon flow condition.
5) Submission of monthly discharge measurement report including site photographs of measurement works and findings;
6) Equipment Used:
• Gurley Cup-type Current Meter- 4 Set;
• 75/35/25-pound fish weight;
• 60 and 45 m long sounding reel;
• Bank Operated Cable Way Accessories- 2 Set
• Wading Rod set- 4 set and
• Four-wheel type crane with pulley system- 2 Sets.
C. Sediment Sampling
1) Discussion with the client about the tentative location to carry out sediment sampling;
2) Collection, gathering and transportation of all the materials and equipment;
3) Appoint and train the site technician to carry out the sampling by Depth Integration Method and Point sampling method and in different frequencies;
4) Development of proper log books to properly keep record of the samples;
5) Sediment Sampling in following location:
a) UAHEP Headworks
• Sediment Sampling by Depth Integration Method using Cable Way for 2 years duration;
• Sediment Concentration Analysis carried out in Lab at Site while Mineral Content Analysis and Particle Size Distribution Analysis in Lab at Office in Kathmandu after bringing dry samples from the site;
• Total Sediment Concentration Analysis: 4880 samples;
• Total Mineral Content Analysis: 100 Nos.; and
• Total PSD Analysis: 100 Nos.
b) IkHPP Headworks
• Sediment Sampling by Point Sampling Method for 1-year duration;
• Sediment Concentration, Mineral Content and Particle Size Distribution Analysis carried out in lab at Office in Kathmandu after bringing filtered samples from the site;
• Total Sediment Concentration Analysis: 474 samples;
• Total Mineral Content Analysis: 50 Nos.; and
• Total PSD Analysis: 50 Nos.
6) Monthly progress report preparation and submission;
7) Equipment used:
a) Polylab bottles of 0.5 L and 1 L capacity;
b) USGS Depth Integration Sampler;
c) Bank Operated Cable Way Accessories;
d) Filtration system and weighing accessories;
e) Drying Oven;
f) Trinocular Stereo Zoom Microscope; and
g) Beckman Coulter Particle Size Analyzer of range 0.4 micron to 2000 micron.
D. Water Quality (Hardness Test)
1) Collection of Water Samples from the following location in monthly basis:
• UAHEP Headworks (24 samples in 24 months duration)
• IKHPP Headworks (12 samples in 12 months duration)
2) Transportation of the Water Samples from the site to Kathmandu and then Analysis of those samples; and
3) Report Compilation and Submission.