BLACKWALL REACH.
The figures are as follows:—
| Gallons per day. | |
|---|---|
| From the River Lea | 52,500,000 |
| ” wells in the Lea Valley | 40,000,000 |
| ” wells in the Kent Co.’s district | 27,500,000 |
| ” the River Thames | 185,000,000 |
| Total | 305,000,000 |
So that two-thirds of London’s water supply comes from the Thames; and as the other sources named above cannot be expanded for future requirements, it is evident that for the increasing demands of London either the Thames or some more distant source must be looked to.
The Royal Commission on the water supply of London estimated that in 1941 these requirements will reach 423 million gallons per day, so that at that date 303 million gallons must be obtained from the Thames or elsewhere.
Now if the Thames is dockised, and the tides kept out of the river, it is evident that much less upland water than is now considered necessary will suffice to keep the river lake fresh and clean, because all sewage and effluents entering the river will be carried directly down to Gravesend; there will be no muddy foreshores and no stirring up of the river mud by the tidal scour.
The river will be, in fact, in exactly the same circumstances as most large lakes—that is, a large body of fresh water, having a main inlet of fresh water at one end, many small inlets along its banks, and one main outlet at its lower end at Gravesend. Such lakes abound all over the world: they are the purest of all waters and never become stagnant.
It is proposed, therefore, that the Thames lake should be regarded as a storage reservoir, so far as water supply is concerned. It will contain sufficient for 320 days’ supply, even at the estimated requirements of 1941; for to whatever extent its waters may become contaminated at and below London, these pollutions cannot work back up the river towards Teddington. It follows, therefore, that between Teddington and London water may safely be drawn off for town supplies, or the supply may be taken as now from above Teddington.
An inspection of the table of flow over Teddington Weir on page 3 will show that in the winter and spring enormous quantities of water, above the quantity considered necessary for scouring the river, flow down and are lost.