‘WAR DIARY. ARMY HEADQUARTERS, INDIA. […] I.E.F. “D”. Volume 14. PART II. (From 16th to 30th September 1915.)’ [‎68r] (140/276)

of time. The north head of the Khor Abdulla provides a very suitable outfall
for the main drain, and was chosen by Sir W. Willcocks for this purpose. If
the alignment for the main drain proposed by Sir W. Willcocks and shewn
on map. 76 were adopted it would be necessary to provide syphons under the
main irrigation channels. By locating the drain on the inside of the protective
embankment, however, the syphons would be avoided, and if the irrigation
system were extended still further into the desert the drain could serve as an
irrigant and a new main drain made inside the new protective embankment.
10. The proposals suggested in paragraphs 7 to 9 of this report are illustrat-
Ultimate development o t the scheme. ed , ° n the . accompanying tracing, scale
1,100,000, irrigation channels being shown
in red and drainage channels in green. As already stated the arrangement of
channels is merely intended to indicate the general nature of the scheme and
the alignments shewn are not, at this stage, proposed for actual adoption. The
system proposed here would readily lend itself to linking up with a main
supply canal such as that proposed by Sir W. Willcocks when the times
became ripe for the inauguration of the more ambitious barrage scheme, and
practically no superfluous expenditure would be incurred by developing the
tract in the manner now suggested. 11
11. Limiting the tract under consideration, for present purposes, to the
Approximate estimate of cost. present cultivated area lying within the
35,000 hectares included in Sir W. Will
cocks’ preliminary scheme, it is considered that about 16 sluices at Us. 25,000
each would suffice costing in all about Its. 4,00,000. To this a further sum of
Us. 2,00,000 should be added for the cost of bunds and channel improve
ments, making a total of Rs. 6,00,000 for works only, adding 33J per cent, for
establishment and contingent charges brings the total to Rs. 8,00,000. The culti
vated area affected as determined from Sir W. Willcocks’ maps (the only ones
available for the purpose) is about 10,000 hectares or 25,000 acres so that the
incidence of cost per acre would amount to Rs. 32. The extra cost of extending
irrigation to the remaining 25,000 hectares or 625,000 acres is estimated in the
following manner. If the bed of the canals be placed at mean sea level, the
176
minimum depth of water in them would be about 4 feet. With this depth the
theoretical velocity of propagation of the tide wave along the canals would be
nearly 8 miles per hour, frictional resistances would reduce this velocity some
what but it is considered that the actual wave velocity would be sufficient to
ensure the maintenance of canal surface level at only a little below high water
level in the tideway. The bed level suggested would entail a mean depth of
digging of about 7 feet. A suitable bed width for canals spaced miles apart
would be 40 feet. With these dimensions the canals would cost about Rs.23,000
per mile, including cost of establishment and contingencies. Each mile of canal
would serve an area of square miles or 960 acres. The incidence of cost per
acre would thus be about Rs 24 and the total cost of the canals for the irrigation,
of 62,500 acres would amount to Rs. 15,00,000. An efficient drainage system
would probably cost about Rs. 5,00.000 including the cost of a tidal sluice at
the outfall of the main drain into the Khor Abdulla. The total cost of the
entire system irrigating the full area of 87,500 acres w r ould thus amount to
Rs. 28,00,000. To allow for interest charges and unforeseen expenditure, how
ever, this figure should be increased by about 50 per cent, which would bring
the estimated cost to Rs. 42,00,000 and the incidence of cost per acre to Rs. 48.
The cost of the watercourse system is not included in the estimate since it
would, as in India, be made by the cultivators or at their expense.
12. Sir W. Willcccks estimates the annual returns from his scheme at about
Rs. 7-8 and maintenance charges plus
Financial aspect. working expenses at about Rs. 1-8 per
commanded acre. In consideration of the fact that the irrigation would be lift
and not flow, however, with the system now under consideration, no more than
half flow rates or Rs. 3-12 per acre could fairly be assessed. The maintenance
charges and working expenses would be less in this scheme, probably about
Rs. 1 per acre. The net annual returns are estimated in this manner to be
Rs. 2-12 per acre which is 5f per cent, of the estimated figure of cost.
13. The financial aspect of the barrage scheme will entirely depend on the
area brought within its scope, since the
Cost financial aspect of ulhmate scheme. ^ commai)ded area the l ess ^jU
be the incidence of cost per acre of the barrage and the embankments^