Development of a Distributed Runoff Model for Pakistan: A Tool for Identifying Optimal Micro-Hydro Siting
Certain sources suggest that 10MW of the currently estimated 300MW potential for microhydro in Pakistan has been developed; other sources estimate the total potential of small hydro in northern Pakistan to be greater than 500MW. Despite the existence of these estimates, there does not currently exist a quantitative metric, and associated distributed runoff model, that (1) is sufficiently high-resolution, (2) forecasts changes in interannual runoff over the lifetime of future hydro installations, and (3) combines these attributes with a Digital Elevation Model to precisely estimate the distribution of power potential. The present study will fill this knowledge gap, promoting the optimal utilization of Pakistan's national hydropower resources.
In the past, high-resolution models have not been practical for areas which, like Pakistan, have sparse meteorologicalmeasurements; however, more physically representative models are now possible due to advancesin climatological downscaling techniques. Through this modeling framework, better gridded time-series of runoff are derivable for the past 100 years, which enables long-term trends and variation in monthly runoff to be analyzed at a higher resolution than previously possible. Snow storage and glacier contributions to runoff must be forecast to estimate future viability of microhydro installations because their contributions account for over 50% of the stream flow to more than half of the tributaries to the Indus River. Several groups have now made available high-quality digital maps of glacier extent. This allows long-term changes in glacier volume to be predicted and the associated eff ects on hydro power production to be quantified. The final portion of this assessment study is to develop a programmable metric for optimization of microhydro unit siting. The metric will likely take into account not only the power potential at each cell but also parameters such as optimal efficiency ranges of the available microhydro units. If there are other human considerations, such as proximity to a village or existing electricity transmission infrastructure, these could also be included given appropriate input information.
