What are the possibilities of these problems being faced in the SSP command? A preliminary study called "Regionalisation of Narmada Command" ( ORG 1982) divided the SSP command area into 13 agroclimatic zones ( Map 2), and classified them into irrigability classes as shown in Map 3. These irrigability classes are based on several soil parameters including the composition of the soil and factors related to drainage. The Soil Survey Manual of the Indian Agricultural Research Institute recognizes six irrigability classes:
Areas classified as Class III are moderately prone to waterlogging, whereas Class IV-VI have severe waterlogging problem under sustained irrigation. It is possible to calculate the SSP command areas under different irrigability classifications from Map 3. The results are shown in Table 1 and 2.
Less than half the command area can be called "suitable" for irrigation. 25.6% of the command area has severe limitations for sustained irrigation (Class III), and 26.5 % of the command area is not suitable for sustained irrigation at all. In other words, 52% of the command area faces high to very high probability of waterlogging and salinisation if the SSP is completed. (It should be emphasized here that the preliminary land classification done by ORG (1982) is for the gross command area, and not the culturable command area.)
An additional factor is that the main soils in Z 7-9 are medium deep black soils, while Z 2-4, have substantial areas of black soils ( ORG 1982). Black soils are known to be unsuitable for sustained canal irrigation, as their high clay content gives them a propensity to get waterlogged. The experience with the Ukai dam, just south of the proposed SSP system, is illustrative. The Ukai command has substantial areas of black cotton soils. Before canal irrigation (1957-58) only about 100 ha (less than 0.5% of the command) reported waterlogging, but by 1991, over 77,000 ha had waterlogging even in the pro-monsoon season ( CD Patel 1993).