VARIABILITY AND PREDICTABILITY OF WATER SUPPLY 137 
into two areas for water-boring purposes. The difference in the 
two areas is concerned chiefly with the charges levied for holes 
drilled by government machines, drilling in proclaimed areas 
being on a ‘“‘no water—no payment” basis, and when water is 
found the rate payable is based on a sliding scale calculated on 
the quantity of water obtained and the footage drilled. In non- 
proclaimed areas drilling is charged for at a fixed daily rate, but 
rebates are allowed which in practice make the actual charges 
very reasonable. 
As regards estimates of volume and rate of natural recharge of 
ground waters, none of the territories considered is sufficiently 
well developed to have acquired the necessary detailed geological 
and hydrological data to enable general estimates of this nature to 
be made; locally, however, the requisite data have been built up 
for particular limited projects, and on the basis of these data 
estimates of volume and rate of recharge have been prepared and 
put to practical use in the development of various schemes for 
township and other water supplies. 
§. Within a Given Watershed, to What Extent Can the Water 
Sources and Water Yield Be Determined? In the better developed 
territories the necessary data have been acquired regarding water 
sources and water yield for particular projects, such as town water 
supplies and hydroelectric and irrigation works. In the less well- 
developed territories the information of this nature available is 
almost nil, and 1s confined to minor local projects and scanty 
short-term records. In general, in relation to the vast areas and 
potential involved, the amount of hydrological data at present 
available is small indeed. Within the last few years the British 
east and central African territories have greatly augmented their 
hydrological staffs and have provided for the collection of standard 
data on a scale never before attempted. This essential step has 
been taken because of the rapid development of these territories 
and of the urgent realization of the need for such data for many 
purposes. The necessity to provide water supplies for the larger 
townships, and to prepare the great hydroelectric projects asso- 
ciated with Victoria, Albert, and Nyasa lakes, and the Zambezi 
and Kafue rivers has proved an immense incentive to the develop- 
