DESCRIPTION OF THE PROJECT AREA
1. General
 
            The project area is illustrated in Figure 1 on page 3. It covers the Mahaweli Ganga basin, the adjacent basins of the rivers of the north-central part1 of the country and of the Maduru Oya. The area is bounded by the watershed of the Mahaweli Ganga in the south by that of the Maduru Oya in the south-east and of the Kala Oya in the south-west. In the north it stops at the border of the zone where groundwater is available in sufficient quantities to meet irrigation needs. The total area of the project is 9,880 square miles ; this is 55 percent of the Dry Zone, and 39 percent of the entire island. Its present population (1966) is about 400,000.
 
2. Climate and Hydrology
            Temperatures are generally very even throughout the year in Ceylon
. Mean temperature is high on the coast (80-820F); in the hills it falls off at a steady rate of 10F for each 330 feet in rise.
            Monthly rainfall shows substantial seasonal variations (see Table TV-I). Total annual rainfall is unevenly spread over the country, because of the effect of the mountains. The year has two maha seasons, locally known as the Maha, (October, to March) which is wet, and the Yala (April to September) which is comparatively dry.
 
TABLE IV-1
 
Monthly Distribution of Rainfall
 

            Oct.   Nov     Dec.    Jan.   Feb.     Mar.     Apr.     May.    June.    July.     Aug.     Sept.      Annual
 
Inches 8.34 12.80  15.59 12.54   5.55     4.11     6.02     3.16     0.39     1.19     2.31     3.00       75.00
 

The estimate irrigation needs, rainfall and the potential consumption of water (evapotranspira­tion) must be compared. In this context, the project area can be divided into three regions ; the lo~ver basin of the Mahaweli Ganga ; the north-central part of the country ; and the upper basin of the Mahaweli. The first two regions are in the irrigation zone ; the third is a catchment area of the main reservoirs.
 
Mean precipitation in the upper basin of the Mahaweli Ganga reaches approximately 90 inches per year, the seasonal distribution of rainfall being fairly uniform.
 
The mean annual precipitation (for 94 years) in the irrigation zone is 75 inches in the lower basin and 57 inches in the north-central part ; during dry years, mean annual precipitation drops to 60 and 46 inches respectively.
 
However, in the dry (Yala) season, both regions of the irrigation zone get more or less equal amounts of rainfall, ranging between 10 and 12 inches, during critical dry years. Owing to this fact, the volume of effective precipitation may be regarded as the same for the whole zone of irrigation.
The term “north-central part” (sometimes abbreviated to NCP) is used, throughout the report, to refer to a region including the North and North-Central Provinces of Ceylon.
 
Effective precipitation is that part of rainfall which is directly available to crops. For the purpose of this study it was assumed that daily rainfall of over 0.2 inch (5 mm), which is taken to represent potential evapotranspiration under local conditions, cannot be absorbed by plants. The excess water either runs off or is lost by deep drainage once the soil is saturated. Effective precipitation values, based on this assumption. for selected drought years at various stations, are shown in Table IV-2.
 
TABLE IV-2
Effective Precipitation in Typical Drought Years
 

Station and Year                    Oct.    Nov. Dec.  Jan.  Feb.  Mar. Apr.  May  June July  Aug. Sept. Year
                                                                                       inches

Polonnaruwa 1958/59
     P.1                                     8.35       8.93     15.65   10.55   0.60     0.56     3.80     1.15     0.85     0.00     1.18     0.68     52.30
      E. P. 2                                             4.15       4.16     4.50     4.25     0.55     0.50    3.20     1.10     0.80     0.00     1.10     0.65    24.96
Maha Illuppallama 1956/57
      P.                                                     5.13       7.20     5.08     2.63     3.33     0.42     923      6.65     1.18     0.10     0.12     1.51     42.58
      E.P.                                                 3.80       4.09     3.78     2.40     2.90     0.40     4.20     4.05     1.10     0.09    0.10     1.15     28.36
 
Kal Aru 1947/48
      P.                                                     9.80       2.94     24.51   8.42     1.70     4.12     1.39     0.39     0.00     1.36     1.42     1.37     57.42
      E.P.                                                 4.22       2.62     4.96     4.15    1.60     3.38     1.32     0.35     0.00     1.29     .35       1.30     26.54
 
Sangilikandarawa 1947/48
        P.                                                   14.5       45.65   11.78   3.14     0.00     0.58     5.83     1.53     0.10     1.31     1.34     0.01     45.81
        E.P.                                               4.45       3.91     4.30     2.70     0.00     0.50     3.95     1.45     0.06     1.25     1.26     0.01     23.84
 
Horawapotana  960/6 1
        P.                                                   5.28       13.05   4.02     16.19   7.09     0.52     2.81     2.92     0.00     0.00     0.00     3.05     54.95
        E.P.                                               3.82       4.38    3.30     4.55     4.08    0.45    2.50     2.60     0.00     0.00     0.00     2.65     28.33
 

1.  P. = Precipitation
2.  E.P. = Effective precipitation.
The table shows that annual precipitation in the various zones fluctuates much more than effective precipitation. The influence of differences in climate on the amount of water needed for irrigation in various parts of the project area is therefore unimportant, and may, for present purposes, be ignored. Keeping this in mind, the monthly distribution of effective rainfall shown in Table IV-3 below was used as a working standard.
 
TABLE IV-3
Effective Precipitation Values in Critical Years
 

        Oct.        Nov.        Dec.       Jan.        Feb.         Mar.      Apr.        May        June      July        Aug.       Sept. year
 

0.36     0.38       0.35.        0.20        0.14         0.16         0.19         0.15         0.07         0.06         0.17         0.04     2.27
 

The effective precipitation, the potential consumptive use and the soil moisture deficiency in the irrigation area for the two seasons are shown in Table IV-4 below.
 
TABLE 1V4
 
Effective Precipitation, Potential Consumptive Use and Soil Moisture Deficiency
in the Irrigated Area
 

                                                                                                  Oct.-Mar.      Apr.-Sept. Annual     
 
                                                                                                                           (feet)
Effective precipitation        ..              ..               ..              ..         1.58                 0.69               2.27
Potential consumptive use   ..              ..               ..              ..         3.21                 3.62               6.83
Moisture deficiency            ..              ..               ..              ..         1.63                 2.93               4.56
Percentage meeting requirements                        ..              ..         49%                19%               33%
 
 

TABLE 1V..5
 
Estimated Requirement of Water to make up Soil Moisture Deficiency
 

Mahaweli                North               Total
Ganga and             Central                 
                                                                                                                                   Maduru                  Part
Oya basins
 

A.      Total area—in 1,000 acres                 ..                                                               ..                                                                ..                                       470                         430                        900
           — existing irrigation                                ..                                                               ..                                                                ..                                       110                         136                        246
           — to be newly developed                      ..                                                               ..                                                                ..                                       360                         294                        654
B. Water required to make up soil                                    
                                                Depth in feet
                            Maha season            ..                                                          ..                                                               ..                                                                                                     1.63                         1.63                       1.63
                            Yala season               ..                                                          ..                                                               ..                                                                                                     2.93                         2.93                       2.93
 
—       volume in 1,000 acre feet
                       — Maha season 1                                                                  ..                                                                ..                                           590                       480                     1,070
                       — Yala season2                                           ..                                                        . -                                                                     ..                                  1,380                     1,260                   2,640
              — Total for the year in 1,000 acre feet ..                                                                                                                          ..                                  1,970                     1,740                   3,710
 

I.
    For area to be developed.
2.   For total area.
 
 
 
The additional requirement of water to make up the soil moisture deficiency for the proposed irrigated area is about 3.7 million acre feet. (see Table IV – 5), of which about 2.0 million acre feet are for areas in the  Mahaweli Ganga and Maduru Oya basin. and about 1 .7 million  acre feet  are for areas in the north central part. To this must be added losses due to subsoil seepage in the irrigated areas, losses in the canals, and losses in the tanks and reservoirs. A final adjustment should be made depending on the proposed cropping patent in order  to arrive at the total water required in the irrigation systems.
 
Groundwater of good quality is found on the lower flood plain of the Mahaweli Ganga, and to the north of the project area.
 
There are 44  gauging satiation in the project area, where the stage of the river has been observed regularly for, the last 5 in 25 years Runoff records at several stations appear some what dubious, so they were extrapolated  from existing records.
 
Few observational mend data are available for sedimentation and silt transport. Estimates for reservoir storage losses from siltation and for the moments and of silt in canals are therefore theoretical.
 
3. Soils and Land Suitability Classification
 
Throughout the project area, soils favorable for irrigated agriculture predominate. All the land in the area has been classified according to its potential economic productivity under irrigation. This classification was made on the basis of characteristics, relief and external drainage conditions, following criteria established by the Bureau of Reclamation of the U.S. Department of the Interior, but with modification, so that account could be taken of local requirements and conditions.
 
Within the total area of new land proposed for irrigation development, nearly half a million acres, or over three quarters oh the area, are placed. in Classes I and II. the balance being made with classes III and IV.
 
The class I lands, which extend over some two hundred and seventy thousand areas, or 40 percent of the new lands proposed for development, consist mainly of soils which belong to the reddish brown earth soil group. Hwy are well to moderately welt drained soils with textures varying from sandy clay loams to sandy clay, and with gravelly sub-soils usually occurring at depths of 20 to 25 inches. Soil characteristic, drainage and topography are favorable for a wide range of crops  to be grown during the dry season. although the wet season crops which provide a good soil cover should be grown.. under standing water contract ions, percolation losses are high arid cultivation of paddy is likely to result  a very high water usage. Natural drainage of these mainly upland soils is usually sufficient, although on the lower parts of some slopes drainage facilities will be required.
 
The class I lands, extend over some I two hundred acid twenty-live thousand acres, or 40 percent of the new lands proposed for development, and are located in the moderately wide valley bottoms.  The soils belong mainly to the group of low-humic gley soils and alluvial soils of the floodplains, with tine hornier group predominating. The low -humic gley soils are slowly permeable, and this, combined with their position in valleys, results in prolonged water logging in the wet season. They are the traditional paddy soils of the Dry Zone and are capable of producing high yields of paddy. The poor drainage limits the use of the low-humic gley soils to paddy production in both the wet and dry season, although if drainage could be improved and the inherent salinity hazard overcome, it is possible that other crops could be grown in the dry season under the climatic conditions of the north—central region. The alluvial soils, consisting of imperfectly drained loams in the wide basins and sandy loams to loamy sands on levees, are suitable for a wide range of crops but are affected by flooding. Other soils occurring to a limited extent in the class II land are grumusols (black clay soils) and red-yellow latosols. The physical Properties of the black clay soils, which are very hard when dry and very sticky when wet, limit their suitability to paddy. The red-yellow latosols. which are very deep friable sandy loams to sandy clay loams. have a high  infiltration  rate, low moisture holding capacity, and a low nutrient status. these soils, which only cover some eighteen thousand acres, are most suited therefore to sprinkler Irrigation for, say, as. citrus cultivation.
 
            The value of the class III lands, extend over less than seventy thousand acres, or nearly 10 percent of the  new area proposed for development, is generally limited by the low water-holding capacity and the high infiltration rates of the soils. Loamy sands and sandy barns in the non-calcic brown earth group predominate, with some coarse sandy soils of the old alluvial sandy regosols group.
 
The non-calcic brown earth soils are found on the undulating to level uplands in association with the reddish-brown earth soils is moderately good, expect in shallow depressions. Although cultivation of these soils is currently limited to paddy, they posses a moderate natural productivity potential, rated at two—thirds of the productivity of the reddish—brown earth soils of class I, and with good management they can produce the same range of crops. The imperfectly and poorly drained soil associates found in this class are best used for paddy.
 
Class IV lands extend over less than 10 percent of the proposed new area. The shallow sandy soils of these lands over-lie strongly alkaline heavy-textured subsoil and are found in the bottom of moderately wide valleys, where they occur in association with the low-humic gley soils, and on the coastal plains. With a plentiful supply of water these lands could be reclaimed and used for paddy or pasture.
 
Assuming flood control on the alluvial soils of the flood plain and attention to improved drainage particularly in the lowland areas, about two thirds of the new lands are suitable for the production of a range of crops. Cultivation of the remainder is largely limited to paddy production or pastures, with a small area stilted to citrus. ‘the existing irrigated areas which lie within the command of the proposed irrigation systems, and which are largely devoted m paddy production, consist mainly of the low-humic gley soils of the Class II lands with a small percentage of the reddish-brown earths, and non­calcic brown earth soils found in association.
 
4.  Present
Land
Use
General
 
Within the project area the laud classified as suitable for irrigated agriculture covers sonic 1.5 million acres of which about 1.2 million acres are undeveloped forest lands, owned by the State, and 300,000 acres are currently under cultivation. About 85 percent of the cultivated land is in holdings not exceeding 5 acres. Irrigation is provided for approximately 272,000 acres. The population is mainly concentrated within the irrigated area.
 
Sonic 252 acres, or 93 percent of the irrigated area, is used for paddy. Of the remainder 12,000 acres are planted with subsidiary crops (chilies, onion, vegetables, groundnuts) and 7,700 acres with sugar cane. The soils of the irrigated land are mainly low-humic gley soils and alluvial soils.
The present and proposed distribution of land in the project area are as shown in Table IV-6.
 
Irrigation conditions 
 
Though irrigation is necessary in both climatic zones of Ceylon
, its purpose and conditions at operation in the Wet Zone are not the same as in the Dry Zone. In the Wet Zone, irrigation is provided mainly for rice, to supplement the generally adequate natural water content of the soil, during brief dry spells. Water duties are thus low. Since water resources are copious in the Wet Zone, while irrigable lands are scarce, nearly all the land suitable for irrigation in the Wet Zone is under irrigated cultivation, throughout both seasons.
 
In the Dry Zone, irrigation is essential to supply the water requirements of crops. Water has to be supplied uninterruptedly on a scale almost equal to the full rate of water consumption of the plants (see Section 2 above) In contrast to the Wet Zone, the Dry Zone has abundant irrigable land, but lacks water. Existing irrigation systems in the Dry Zone are as a rule in full operation during the Maha Season only; in Yala only 35 percent of the irrigable area in the north and 75 percent in the southwest can be provided with irrigation.
 
Major irrigation schemes are represented by systems of engineering and semi-engineering type The water supply to these is generally based on restored (or, in rare cases, new) reservoirs of low head and with long earth dams. The main contour canals are not lined and, having an embankment only on the downhill side, they receive water from the catchments lying above. This inflow compensates for the seepage and evaporation losses, which are considerable due to sizeable wetted perimeters. Distributaries and field networks are almost always unlined, which brings the losses up to 35-45 percent of useful water supply to the fields. A considerable part of these losses is attributed to the escape of water through breaches in banks and field ridges, to outlet gates being out of order, or to excessive water application to crops. Although the systems have more or less satisfactory control structures,
 
During drought when the irrigated systems are inoperative, the Rajarata peasant resort to chena cultivation. Make shift watch towers at a height safe from wild animals, help keep vigil. Chena cultivation involves slashing and burning forest cover, and is essentially destructive. It will be a thing of the past when advanced agricultural practices are introduced by the Mahaweli Development board along with irrigation water in to the new area developed under the Mahaweli Development Project. 
 
            There is no proper management of water distribution in the fields. The drainage network does not permit barge of flood waters for which reason a portion of irrigated lands (5-10 percent) is periodically in a state of over-moistening.
 
Minor irrigation schemes consist of small-scale systems (tap to 50 acres in extent.) Their supply is received from small reservoirs or “tanks” which store and regulate the yield from rainfall.
 
The active capacity of such minor tanks in the Dry Zone provides, as a rule, water for irrigation only during the wet season. There is practically no control arrangement on the irrigation networks, which are very simple. However, due to the chronic shortages, water is spent more economically as compared with the major schemes. Generally speaking the efficiency factors of both types of systems are almost equal.
 
The systems which are rain fed have no storage ; rainfall is accumulated here instantly on “liyaddas” (small paddy plots). Sonic additional water is supplied from the canals which run along slopes of hills, intercepting minor streams and also the surface runoff from the catchments.
 
Non-irrigated areas
 
The non-irrigated area is estimated to extend over 28,000 acres and consists mainly of upland arable holdings, on the reddish-brown earth soils, and a limited area of ‘chena’, or shifting cultivation, within the forest areas. Much of the non-irrigated land is planted to rainfed paddy, various cereals including maize, sorghum, elusine (kurakkan), and a range of vegetables. The remainder is under various tree crops, or pasture. To date most of the upland cultivation developed under colonization schemes has not been very successful. h-ugh but poorly distributed rainfall, shortage of labour in relation to holding size and the settlers’ lack of experience in growing crops other than paddy, have contributed to the unsatisfactory development. In the northern area, however, particularly in Vavuniya, an intensive system of mixed farming has developed on small holdings of about 2 acres under lift irrigation and a range of crops, including vegetables and tobacco, are successfully grown. No signi­ficant increase in ‘chena’ cultivation is expected in the near future.
 
Lack of reliable supply of water, poor weed control and lack of erosion control measures, are major problems in the non-irrigated upland areas.
 
Limiting factors to more intensive production of paddy
 
Double cropping of paddy land is one of the most important practices for maximizing produc­tion. The second paddy crop in the Yala season as obtained only if entirely irrigated, whereas the first Maha crop may be mainly rainfed with only supplementary irrigation. If the planting of the Maha crop is done early enough to take advantage of the rainy season, it can be grown with less irrigation, and water can be stored for the production of the second crop.
 
There are a number of major obstacles to effective double cropping of paddy. The first is the lack of a reliable supply of water at the beginning of the Maha season. Although some land prepara­tion and sowing does take place with the early rains, much of the field preparation is delayed until irrigation water is released from the tanks. Where land is prepared as soon as the soil is sufficiently moist from the first rains, about 2 acre feet of water can be saved which would otherwise be used for land preparation, and mechanization is easier and more economic. There is however an undoubted risk element, unless supplementary irrigation water as immediately available. Further, average yield. tend to be lower than those from fields which are prepared following complete inundation, due to the more abundant weed growth. However water is not released from the tanks until they are sufficiently lull and the rainy season is well under way. This limits the time which can be allocated to field preparation, resulting in poorly prepared land, delayed seeding, wastage of rainwater and inadequate storage of water for the Yala crop. Many of the settlers who came from the Wet Zone are accustomed to the system of “wet” paddy cultivation and will delay land preparation until water is released from the tanks, even if this means leaving the field tallow because the tanks have filled too late in the season.
 
Although tractor cultivation is used in the project area, the second major obstacle is lack of sufficient arid suitable traction power to ensure timely cultivation.
 
TABLE  IV - 6
Present and proposed distribution of land
 

                                                                                                                        Area in thousands
                                                                                                                               Of acres     
A.      The whole project (9,880 squire miles)                                                                      6,320
B      Area with soils classified as suitable for irrigation                                                         1,500
(i)   Undeveloped (forest)                                                                                          1,200
(ii)  Presently cultivated                                                                                                 300        
      (a)  Irrigated                                                                                                          
          -     paddy                                                                                 252
          -     subsidiary crops                                                                   12
          -     sugar cane                                                                            08              272
 
(d)  Rainfed                                                 
         -      paddy                                                                                  10                            
         -      subsidiary crops                                                                   07
pasture                                                                                05                
coconut and other tree crops                                               06                 28
 
C.      Total area proposed for irrigation development                                                               900
 
(i)      Existing irrigated areas within the command of the proposed
       irrigation systems
                -     in the Mahaweli Ganga and Maduru Oya basins                  110          
  -                                          in the north-central part                 136               246
 
(ii)                New areas to he irrigated
-      in the Mahaweli Ganga and Maduru Oya basins                        360
-      in the north-central part                                                             294               654
(iii) Assumed cropping pattern in the new areas
paddy (paddy-paddy-legume)                                            190
mixed (paddy-cash crops)                                                  105
                                cash crops in rotation                                                         327    
irrigated past tare                                                                 20
sugar cane                                                                           12                654
 
D.      Area presently cultivated, but lying outside the outside                                                    
         of the pro­posed irrigation systems (300 minus 246 thousand acres)                                   54
 
E..     Balance underdeveloped land to continue tinder forest                                                    546
 

A third obstacle which tends tea he perpetuated by the lack of an early, reliable supply of water for the irrigated plots. arises from chena cultivation. Under this system the farmer makes of the early rains for various tainted crops in the adjacent unleased areas, and this tends to delay the start of the Maha paddy crop.
 
Under the present system of paddy cultivation, irrigation and water management, the available permits an average intensity of cultivation equivalent to 1.37 crops of paddy per year only.
 
Limiting factors to increases in yields of paddy
 
The average yield of paddy in both the Maha and Yala season is about 40 bushels per acre. The low yields are largely due to two factors. The first is the shortage of an early and assured supply of irrigation water, and the second is the traditional practice of broadcasting, without adequate weed control, a practice which is carried out over some 95 percent of the paddy fields. In Vavuniya,  and  Other districts shortage of an early and assured supply of water is especially acute, the yields are as low as 33-37 bushels in the Maha season. For irrigation systems having a more assured water supply (e.g. Polonnaruwa ) yields of 57 bushels per acre acre obtained in the Maha season. A substantial increase in yields is observed on farms where the seedlings are transplanted. the average yields thus obtained in the Maha season being in the order or 77 bushels per acre. Shortage of labour however is likely to be a limiting factor to widespread adoption of transplanting. and row-seeding, together with improved weed control measures, may well be the most practicable alternative.
 
Weed competition, resulting from insufficient tillage (caused in tern by lack of water at the begining of the season and shortage oh traction power and labour) as also a significant limiting factor to. high yields. This as already stated, is aggravated by the general practices of broadcasting. chemical control of weed growth is limited but is Inn-easing, although the lack at’ foreign exchange for the purchase of the chemicals and the necessary application equipment is a restricting factor, as is the high cost of  the chemicals to the farmer.
 
Although there has been au increase in the use of fertilizers over recent years, the area fertilized is restricted and the rates of application are low. Fertilizer consumption in five main districts of the project area in 1965/66 ranged between an average of 64 lb. per acre of product (ammonium sulphate, rock sulphate, and muriate of potash) down to 12 lb. per acre. The current ‘recommended rate per acre for paddy is 224 lb. of ammonium sulphate, 112 lb. of rock phosphate and 56 lb. of muriate of potash (45N-35 P2 Q-28 K20).
 
The average yield increases in bushels obtained from a large number of trials and demonstrations fertilized at this level are as follows —
TABLE IV-7
Summary of Effect of Fertilizer on Paddy Yields
(yields in bushels  per acre)
 

                                   Maha              Yala                Maha              Yala        Maha
                                   1964/65          1965               1965/66          1966       1966/67
 

0-0-0 ..                        55.6              51.0                 51.6              40.8         50.1
45-35-28                      78.2              66.5                 72.6              57.8          74.8
 

Percent increase           40.6               30.4                 40.7              41.7           49.3
 
1.  One Bushel = 36.4 liters.
One Bushel of un milled rice weighs 46 lb.
These results were obtained in areas with a more assured supply of water, and where the standards of cultivation practices were above average.
 
Further economic increases in yield can be obtained by raising the application of plant nutrients per acre from the current recommended level to 60 N - 40 P2 O~. - 30 K2
0 lb. per acre. Recent Increases in use are due to the high Government subsidy for fertilizers used on paddy, and also to trials and demonstrations conducted by the Freedom from Hunger Campaign.
 
Considerable progress has been made in the introduction of improved crop varieties. The widespread use of the four-month paddy variety H-4 has contributed to production increases. However the realization of the full potential of this and other improved varieties will depend on an adequate supply of water and the adoption of improved agricultural practices including the use of fertilizer s.
 
Problems of diversification of cash cropping
 
It should be noted that the experience of the majority of peasant farmers is limited to a traditional system of paddy growing which is orientated towards a subsistence rather than a market economy. In addition to the technical problems which need to be ‘solved before extensive diversification of cash cropping can be introduced, including control of flooding and soil erosion and the provision of adequate drainage, the problem of directing farmers’ interest towards substantial cash crop production should not be underestimated. current yield selected crops other than paddy are shown in Table IV-8 below.
 
TABLE IV-8
Current Yield of selected Crops
 
 

Crop                                                                                  Yield in cwt. Per acre
 

            Shallot Onions                                                                                        90
            Bombay
onions           ..                                                                        80
            Chillies                                                                                                    8
            Groundnuts                                  ..               ..                                         8
            Green-gram                                                                   ..                        5
 

An increase in the area under cropping and in the yields per acre will require particular attention to be given to market incentives, transport, storage and processing facilities, and to an enlarged and well trained extension service. Development, even then, is likely to be slow.