Regional estimates of the degradation of dry lands of Sindh support the conclusion that desertification is a major problem and is growing in magnitude. It is a malignancy undermining the food producing capacity of these otherwise fertile and virgin land resources.
The dry lands normally receive annual rainfall between 80 and 350mm, with inter-annual rainfall variability between 50 and 100 per cent. Some scattered vegetations permit low intensity grazing, but no rain-fed agriculture can be maintained on continual basis.
The term dry land is easy to understand in a general sense, but is difficult to define in precise terms. The same is also true for concepts such as aridity and drought. With all of these terms it is water shortage which is the critical variable, though other factors are also important. In this context, the term dry land involves a much broader interpretation than the case with more commonly used term arid land.
The dry zones of Sindh are classified as subtropical deserts. These constitutes the Thar region, the Nara region, including portions of Sukkur, Khairpur, Nawabshah and Sanghar districts, and Kohistan region encompassing parts of Dadu district and stretches along the Indus delta, including parts of district Malir of Karachi.
Since no major water resource development project has ever been started in these drought prone dry lands of Sindh, rainfall is still a growing factor for the entire area. Because of paucity of rainfall there is no perennial stream in the area. Apart from rainfall, the only other source of water is well.They play a decisive roll in the socio-economics of these areas. In an extremely dry season reservoirs may dry up and the level of water in the well falls beyond the lifting capacity of pumps.
Due to specific physical characteristics of dry lands, seepage rate in these dry areas is very high. Lining of water courses is a necessity in these areas not only in the interest of optimum utilization of water, but for the sake of its conveyance to all parts of a tubewell command. It has been proved in various scientific studies that seepage loss in an unlined channel is more than six times higher than a lined channel.
Keeping in view the importance of well water for these areas we will have to realize the fact that without initiating a comprehensive groundwater irrigation development programme for dry lands of Sindh, the goal of agriculture development and self-sufficiency in foodgrains and a self-stable economy of this drought-affected areas could not be achieved.
Utter dependence on rainfall in dry lands is the main cause of all sufferings and miseries as there has not been sufficient rainfall in these areas for a long time. One and the only solution to such an acute situation is to find a reliable and continued source of water.
In the absence of required amount of rainfall on continual basis in dry lands of Sindh there is an urgent need to develop a contingency plan that could help in drought-like situations. What is quite obvious from the survey is that a single agreed strategy of importing water in these areas is best suited to develop these dry lands. Floodwater canals to these dry areas of Thar and Kohistan can only relieve masses of these areas from the hardships on continual basis.
Extension of Nara canal network to Thar areas and connecting flood/storm water channels of Kohistan region with Manchar lake for diverting floodwater of the upcountry during high flood season can convert these dry regions into an oasis. Fortunately, it is a blessing of God that topography of the area allows these ambitious projects which are likely to change the fate of these dry lands.
Analysis of monsoon pattern of the country reveals that rainy season in the northern areas starts very early then in Sindh. More often it happens that floodwater starts reaching Sindh (Sukkur barrage) before rainy season in dry lands of Sindh. Therefore, proposed floodwater canals can bring surplus upcountry flood water to these water starved regions at a time when people of the area are in dire need of water.
The floodwater, thus reached to these dry areas through floodwater canal can be used for recharging the dried wells, storing water in ponds for human and livestock use and for crop production. The water storage ponds can be lined with polyethylene plastic film to eliminate high seepage losses of desert areas.
What seems to be clear is that capital investment required for undertaking this project might not be recovered solely from the agriculture activities in these areas. If the government decides to fund such a project for these backward areas, it would have to be thought of as a subsidized regional development programme rather then a straight-forward economic investment.
Although groundwater irrigation plays a significant roll in the socio-economics of the dry lands of Sindh, unfortunately adequate attention was not given to the groundwater development in these areas owing to long experience of the canal based irrigation in the province, uncertain assessment of groundwater and constraints on energy required for pumping.
In the nutshell, the groundwater irrigation development in dry lands of Sindh has not been commensurate with the need and the potential. Whatever reforms that have been undertaken here in dry lands of Sindh were politically motivated rather than for social reasons, and it is therefore, not surprising that many of the poorest people have benefited a little from these reforms.
Use of groundwater for irrigation in dry lands of Sindh is both attractive and imperative on several accounts. After a long dry-spell of almost a decade the quantity and quality of groundwater reserves of these areas has been affected badly. This is largely because of high rate of groundwater use relative to natural recharge rate of aquifers.
For years most of our planners have been advocating the idea of conserving rainwater through the consideration of reservoirs in Thar and small water collection dams and slow action dams in Kohistan where a good number of rains rivers flow during rainy season.
Proponents of such water collection dams in Kohistan region do not take into account the fact that availability of rainwater is not sufficient for building a dam. There are certain other factors, particularly catchment area characteristics, silt load, etc., which are of prime consideration. There are certain examples within our country when such a dam project which was constructed without considering these factors rapidly filled with silt or else did not provide as much water as had been predicted.
These planners while floating such an idea of preserving water in ponds, small dams, etc., fail to understand that artificial reservoirs, whatever it may be, pond or small dam, can only be beneficial for a localized place bordering such reservoir or pond. Whereas if we let the floodwater flowing in the storm/flood water drains it will recharge groundwater of a vast area through a complex natural network of underground water movement, thereby benefiting all such wells falling within this network.
Further, if floodwater is dammed it may create complications of water rights between lower and upper riparian of that particular floodwater channel. Moreover, building a storage reservoir may also involve displacement of people who are settled on the project site. The burning case of Chotiari reservoir in district Sanghar may be cited as an example which has been made for the purpose of floodwater stocking.
Therefore, in order to avoid all such manmade complications would it not be better that we let the floodwater flow at its own through a number of storm water drains in Kohistan and let the nature divide the water among the adjoining areas through its subsurface network and enable all stakeholders to fetch it through their individual wells as and when required.
In addition to these floodwater canals to Thar and Kohistan areas we also need to explore option for diverting the RBOD water to Arabian Sea through these storm water drains of Kohistan region. It is required that scientific analysis is carried out to ascertain effect of this marginal water effluent of the upcountry on groundwater quality of Kohistan area.
Giving these changes the government of today has a greater responsibility for the successful management of their dry lands than was the case in the past. As a result it is crucial that a holistic approach with a broad knowledge of environmental issues may be followed to solve problems of dry lands of Sindh. All too often in the past, we have lacked the broad overview needed for the successful environmental planning. In such circumstance it was due to this reason that so many developments projects initiated in the dry lands have not lived up to our expectations.