barriers built to increase the storage facility of stream deposit should thus be built to a height to maximize the storage capacity by the porous medium high dams are built to accentuate the height different of the water level behind and in front of the dam for the sake of an increase of the potential energy of water flow to generating electricity the cost of dam construction is very high the purpose of constructing barriers or partitions 16 across stream valley in an ihc is to store water in porous medium not to generate electricity there is no need to construct high dams and the cost of construction can thus be greatly saved in fact the partitions need not as strongly anchored to the valley bottom in stream valleys of low gradient as a dam the partitions serve the function of raising the groundwater table in the valley sediment and thus to increase the water storage capacity of the sediment behind the barrier the engineering design of the barriers should thus be specially tailored to suit the local conditions one or more barriers 16 can be constructed over the whole length of a stream valley the partitions are punctuated by pipes with coarse gravel so that the.