Poonch River at the damsite drains a catchment area of about 3625 km2. River is gauged near Rahman Bridge by WAPDA from where observed hydrological and sedimentation data was procured for the period 1960-2002. Data related to meteorological parameters such as rainfall, temperature, humidity etc., was obtained from the meteorological station being maintained at Kotli by Pakistan Meteorological Service (PMS).
Mean annual rainfall in the area is about 1310 mm. Average annual temperatures remain as low as 5oC in January and as high as 38oC in June. Mean annual evaporation is of the order of 1430 mm, the highest being in June (229 mm) and lowest in Dec. (46 mm). Mean annual flow of the river at the site is estimated at about 3,995 million cum (MCM). Months of July and August are the months of maximum flow. Nearly 30% of the annual flow occurs during these two months.
The spillway design flood is based on frequency analysis of maximum flows that works out to be 13,340 m3/s. This flow corresponds to a 1 in 100 years event and is used in the design of water-way for the weir structure. The observed flood of record occurred in Sept., 1992 which was 12,150 cumecs. The diversion flood considered in the design of cofferdams is 1,265 m3/s, which is a 25 year frequency event.
On the average, Poonch River brings an annual suspended sediment load of 12.63 million short tons (MST). The average annual sediment load used in the study is 13.90 MST which includes about 10% of unmeasured bed load. Proper arrangements for sediment flushing are incorporated in the Project layout. It is estimated that larger size sediment particle would be deposited in the lower reach of Bann Nullah near the sluiceway thus keeping the power intake free from sediment.
Installed capacity of the Project is selected as 102 MW. Whereas the available net head at the site is 57.5 m. The design discharge is fixed at 194 m3/s which has a flow exceedence of about 18%. Annual energy has been computed using the daily flow data of last 43 years. It is estimated that the annual energy generation will vary between a maximum of 737 GWh to a minimum of 308 GWh. The average annual energy will be about 465 GWh with a plant factor of about 52%. It is also estimated that about 143 GWh can be generated in 4 hr peaking operation whereas, 322 GWh will be available in the remaining 20 hrs.