Allocation of water consumption in multipurpose reservoirs

Abstract

The Intergovernmental Panel on Climate Change Special Report on Renewable Energy Sources represented a benchmark in the assessment of water consumption from electricity production. The numbers for hydropower ranged from very low to much larger than the other renewable technologies, partly explained by methodological problems. One of the methodological shortcomings identified was the lack of guidance on how to allocate the water consumption rates in multipurpose reservoirs. This paper is, according to the authors’ knowledge, the first attempt to evaluate, test and propose a methodology for the allocation of water consumption from such reservoirs. We tested four different allocation methods in four different cases, all serving three to five functions, including drinking water supply, irrigation, flood control, industrial water, ecological flow and power generation. Based on our case studies we consider volume allocation to be the most robust approach for allocating water consumption between functions in multipurpose reservoirs. The spatial boundaries of the analysis should follow the boundaries of the hydraulic system. We recommend that data should preferably be gathered from one source for all functions, to ensure a consistent calculation approach. We believe the findings are relevant for similar allocation problems, such as allocation of energy investments and green-house gas emissions from multipurpose reservoirs.

The Water Footprint of Hydropower Production—State of the Art and Methodological Challenges

“…Choice of allocation method is a known problem from Life Cycle Assessment (LCA)‐based studies, and the basis for allocation in LCA‐studies is often ISO Standard 14044 . According to the authors' knowledge, the study by Bakken et al was the first of its kind that systematically tested out allocation methods as specified by ref. .…”

“…The study tested four different allocation methods in four multipurpose reservoirs, all serving three to five functions, and concluded that volume allocation was the most feasible and robust approach. Economic allocation was found by Bakken et al to be sensitive to selection of economic valuation method, but acknowledged that this method could be useful in those cases where the same economic valuation method was applied across all functions served by the reservoir. Kadigi et al underline that use of economic valuation methods could underestimate the social value of water.…”

“…The methods “Equal weighting,” “Economical valuation 1,” “Primary purpose,” and “Economical valuation 2” allocate in the range 35% to 55% of the water losses to hydropower, while “None to hydro” and “All to hydro” are in the extreme ends allocating 0% and 100% to this function, respectively. The study by Bakken et al showed a similarly large spread in allocation ratios. The studies illustrate that choice of method will affect the assignment of losses to the hydropower production dramatically, which was also underlined by Lampert et al.…”

“…Bakken et al underlined that the recommended volume‐based allocation method will not capture the full complexity of regulations and a hybrid of different methods might provide more reasonable and robust output. The next step in refinement of allocation method might be a methodology that takes into account elements from economic allocation, the priority of the water use from the multipurpose reservoir, as well as the degree of regulation needed by each function.…”

Drivers of water use in China’s electric power sector from 2000 to 2015

“…Prevalent generation technologies include coal, solar PV, wind, hydro and so on. This study does not consider hydropower because the quantification of its water use embodies many methodological disputes and uncertainties, especially regarding the attribution of water use in multi-purpose reservoirs (Bakken et al 2016). In terms of cooling technologies in thermoelectric power plants, air cooling systems, which use air to cool down the steam exiting turbines, use the least water.…”