The sugar industry of British Guiana is conducted on land reclaimed from the sea and from swamps some 200 years ago.
About three-quarters of the area devoted to the crop consists of
rich, heavy, acid, marine clays, in which appear strips and masses of sand, the remainder being organic soil of poor water retentive capacity and low fertility. The present sugar plantations with their land devoted to related purposes are 155,000 acres in extent, of which about 60,000 acres are reaped annually. Five rivers traverse the area and discharge into the Atlantic Ocean. Extensive sea walls, maintained by the Government, give protection from the encroachment of the sea, and river embankments kept up by the estates control the rivers. A small portion of the total area can be drained by gravity at low tide, but the remainder is controlled by pumping, usually by equipment mounted on pontoons or barges.
The land is sub-divided into long strips having frontages to the sea and running inland for several miles. Behind the cane lands a catchment area for irrigation water is maintained by an inde- pendent Conservancy, together with a main irrigation canal run- ning roughly parallel with the coast, from which water is supplied to the plantations. The individual estates are each enclosed by an embankment or empoldering dam. The portion at the seaward end is the " sea dam," those on each side being the " side line dams " and the one at the rear the " back dam." Fields are of 10 to 12 acres in extent, rectangular in shape and surrounded by a polder and canals, each of which is named according to its position. The arrangement of fields is shown in Fig. 13. The canals are of two types, one for irrigation and transport and the other for drainage. The irrigation distribution system is at a higher level than the drainage canals which are larger and deeper.
It has been estimated that each square mile of cane land has 49 miles of drainage canals and ditches, and 16 miles of high level waterways used for irrigation and transport. The disposal of the irrigation water and water derived from rainfall, averaging 80 to 91 in. annually in the two main districts, is very costly. Added to this expense is that of the constant maintenance of canals and dams, most of which is still done by manual labour, though mechanical devices are coming into increasing use. Luxuriant growths of weeds which develop rapidly and deposits of mud and debris which would soon choke the canals have to be dealt with.
The whole system of sugar-cane cultivation in British Guiana is unique and may well be called an amphibious operation. Refer- ence to others aspects will be found in Chapters 2 and 5.
Navigation and draniage c a n a l s are also
[Reproduced from Report of a C o m m . o f Enquiry into
are also shown.
inquiry into the Sugar Industry of British Guiana by permission of the Controller ,H.M. Stationery Office
8o
Local P u m p Drainage
In low lying almost level land with a very slight fall, h i g h volume low lift centrifugal and impeller pumps are often used to supple- ment local gravity drainage during periods of high rainfall when the unaided surface run-off is inadequate. The basic equipment required is mechanically simple, and when properly installed needs very little attention. Diesel or electric power can be used, the latter being preferable as it lends itself to automatic operation of the pumps. Similar methods are used to remove t h e water discharged from a mole- or tile-drained area when natural condi- tions found in low lying lands would otherwise prevent t h e under- drainage system from working properly. The pump discharge can be delivered into a canal raised above ground level, or to a higher point of the land from which it can flow freely away from the drained area. Small portable pumps of high capacity adapted for belt drive from an engine or tractor for temporary emergency drainage at points where this is needed are capable of giving efficient service. Schemes of this type are often used on parts of individual plantations where the whole drainage system is under the owner's control.
Drainage as a Cultivation Operation
The construction and maintenance of field drainage works are essential and important parts of the whole range of cultivation operations in land where natural conditions of soil texture and topography do not allow the speedy and free removal of surplus water from the upper layers of the soil. Drainage must be effec- tive at the proper time, or the success of other work on t h e land may be put in jeopardy. Mention has been made of t h e need to cut the quarter drains immediately the beds and furrows have been formed in the Louisiana method. The cambered b e d system is just as much dependent upon drains being in constant working order even though they may not be fully formed after damage during ploughing. If the drainage is badly impeded after plough- ing and harrowing, the soil may become water-logged a n d lose its tilth, which it may not be possible to restore for m o n t h s after.
Thus effective drainage must be available to remove excess water throughout the period of preparation and cultivation as well as
during the whole life of the crop. The interior drainage of an estate or plantation is the responsibility of the owner.
Conservancy Authorities
Field and farm drainage forms part of the water and soil con- servancy measures which are important to the protection of the land and the welfare of communities. It is rarely possible for a drainage scheme for a plantation to be planned and conducted entirely independently of neighbouring interests, exceptions being small isolated areas with a water course conveniently near which can act as a main drain without interference with conditions lower down the stream; and large areas under single ownership and control where independent and comprehensive drainage works are possible. In a single drainage basin some suitable form of unified and regulated action by all landowners is essential. Examples given are Louisiana, the Florida Everglades and British Guiana, in each of which the safety and success of agricultural operations depend upon the co-ordination of all land drainage in conformity with the requirements of the whole drainage area. The usual system is to appoint conservancy or drainage boards under the provisions of laws enacted for these purposes. Such authorities are given wide statutory powers enabling them to plan, construct, control, and maintain area schemes of main drainage, and to require all landowners within that area to erect and maintain the necessary subsidiary drainage works on their own land.
CHAPTER 6