British Mandate: A Survey of Palestine: Volume I - Page 403

CHAPTER X.

thirty kilometres long falling down to the Jordan rift from Mount Gerizim near Nablus. The losses in the previous earth channels were enormous. The scheme is not yet completed, The inhabitants of the valley are all Arabs. The due completion of the scheme depends on the enactment of the necessary legislation for the control of the distribution.

52. At Jericho there is a small system for the distribution of water to State Domain lands. The difficulties encountered here present another vivid example of the impracticability of attempting to administer an irrigation scheme without powers to prevent the transfer of so-called water rights separately from the land and without reference to the distribution system.

DRAINAGE QUESTIONS.

53. Flooding occurs near the outlet of several of the big drainage wadis. But it is impossible to suggest a cure for this without preparing a drainage scheme embracing the whole catchment area. This divides itself into three parts :-

(a) provision of forest and vegetation cover on the headwater

slopes and steep lands with the object of slowing up run-off;

(b) the factors causing soil erosion and storm run-off;

(c) engineering works necessary to control the floods.

54. There must of course be close co-operation between those interested in conservation of the soil and the irrigation engineers. Probably co-ordination by itself is insufficient. Centralisation of control in a single authority is more likely to achieve the desired combination of effort in drainage areas. There have not yet been collected sufficient figures on which to form conclusive opinions as to the extent and rate of silt erosion in Palestine. Measurements of run-off have in some wadies been taken over only a short period of years, but it seems certain that the run-off is extremely low, and that the proportion of the precipitation which percolates to the underground is large. It is also established that the chief form of soil erosion is that of the top soil of the steep hills being washed off and deposited on flatter shelves below. The measurements, though not conclusive, also suggest that the silt content in the run-off is not excessive, or even large, and that the quantity of soil carried down and lost in the sea is not by any means of catastrophic proportions.

55. For the purpose of drainage study the country has been divided into catchment areas and stations for observing the run-off

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