This week's programme in the series on Man and Science Today.

It's almost inconceivable, with our climate, that we should be in danger of a water shortage. Yet some areas already suffer a semi-drought every summer, industrial development is threatened, and the situation is certainly going to get worse.
There is, of course, no shortage of rain here, but most of it runs to waste down our rivers, and with land at such a premium the construction of new reservoirs can no longer be expected to match the increasing demand. There are alternatives, numbers of them, but each provides the engineers and scientists with a complexity of problems.
Controlling the flow of a river may radically change, even destroy, its wildlife. Placing barrages across our biggest estuaries like the Wash and Morecambe Bay may do the same and more. At Morecambe they are investigating the very real possibility that the ports of Heysham and Barrow-in-Furness may be silted up completely.
Tonight's Horizon looks at the work of our scientists as they try to unravel the problems of providing us with more water.