Land and Water Management Engineering

Land and water are basic resources in agriculture. For successful agriculture, proper utilization of these basic resources is essential. Land and Water Management Engineering broadly implies the application of engineering principles to the solution of land and water management problems. The phrase ‘Soil and Water Conservation Engineering’ is also commonly used to mean the same as ‘Land and Water Management Engineering’. Conservation means the utilization of these resources to sustain a high level of production indefinitely.

Engineering in Land and Water Management:

For the purpose of study of the engineering problems involved in land and water management or soil and water conservation, we may divide the subject into different topics. These are – soil erosion control, moisture conservation, land development, irrigation, groundwater development and wells, agricultural drainage and watershed management. Soil erosion control refers to the protection of soil from erosive action of natural agencies like water and wind. Moisture conservation practices are needed to conserve rainfall for crop production.

Land development refers to reclaiming land from conditions which make the land unsuitable for cultivation. Land grading for making the land suitable for irrigation is also sometimes termed as land development.

Groundwater development and wells deal with the exploitation of underground water resources. Irrigation is defined as the artificial application of water to land for crop production. Drainage refers to the removal of excess water not needed or otherwise harmful for crop growth.

Watershed management refers to a combination of practices to achieve objectives like reduction in floods or reducing the sediment outflow from an area. Another emerging area with which land and water management is concerned is the environmental management. Land and water are major components of the environment and protecting land and water quality is part of land and water management.

Land and Water Management and Agricultural Production:

The different areas of land and water management engineering have a significant role in agricultural production. Increased agricultural production can be achieved either by bringing new areas under cultivation or by increasing the productivity of the areas under cultivation. Land and water management engineering practices have a role in both these alternatives. New areas are brought under cultivation by suitable land reclamation methods.

One of such methods is the reclamation of areas under forests and shrubs, which involves the operations of land clearing and grading. Land under ravines or deep gullies are reclaimed by adopting suitable soil conservation measures. Agricultural drainage helps in reclaiming areas under waterlogged or salt-affected conditions.

Irrigation of areas either reclaimed or already under agriculture has a great impact on agricultural production. Control of soil erosion in agricultural lands, proper design of water application systems, scheduling of irrigations based on crop water requirements, removal of excess water not required by the crops, are some examples of land and water management practices which can increase the agricultural productivity.

For obtaining maximum agricultural production from an area, several factors need to be considered. These include proper land preparation, use of improved seeds, use of optimum dosage of fertilizers, efficient application of water, control of insects and pests and carrying out all agricultural operations at right time.

Land and water management measures form an integral part of the agricultural production technology and are a prerequisite for the efficient utilization or all other inputs. Neglect of or inadequate attention to any of the above-last measures will not only reduce agricultural production but also will lead to poor utilization of other inputs.

In several countries of the Asian region, land and water resources are limited, population pressures are high and a majority of the population is dependent on agriculture and allied professions. Table 1.1 shows the population, land use and renewable water resources for some developing countries.

Soil and Water Conservation:

Soil and water conservation consists of prevention and control of soil erosion caused due to wind and water. It also includes conserving rain water for the purpose of crop production. Soil erosion severely affects hilly areas because of the steep slopes. In hilly areas permanent agriculture is not possible without adopting soil conservation measures.

Landslides and slips are other problems of hilly areas. Water erosion is also respon­sible for continuously washing away the top soil in agricultural lands. Large areas around the world are menaced with soil erosion. Areas under rain fed agriculture are particularly affected by erosion both by water and wind.

The ultimate potential of irrigation from the available water resources is limited. Considerable part of the agricultural production areas will continue to be rain fed. Proper utilization of the rainfall and moisture conservation is very important.

In high rainfall areas, the problem is to dispose the rain water without causing damage to the land where as in low rainfall areas; the problem is to conserve the rain water. Dry farming is a system of soil and water management practices suited to arid and semiarid areas for conservation and efficient use of soil moisture.

In all the countries in the Asian region, soil and water conservation problems exist in varying degrees. It is estimated that out of 194 million hectares of culturable area in India, nearly 145 million hectares are affected by soil erosion. Table 1.2 shows the extent of rain fed agriculture in some countries of Asia.

Groundwater and Wells:

Groundwater forms a substantial part of the total water resources and provides water for irrigation, municipal supply and industrial use. Unlike mineral resources, groundwater gets replenished by the natural process of recharge. Groundwater utilization should, therefore, be properly planned to achieve a balance between replenishment and extraction in order to maintain a perennial supply.

In the recent past considerable advances have been made in all countries of the Asia-Pacific region, regarding groundwater resources development and management. Groundwater has the advantage of being available at the point of utilization. The Economic and Social Commission for Asia and the Pacific (ESCAP) briefly reviewed the situation relating to groundwater issues in the member countries and presented a set of recommendations for management (ESCAP, 1987). Figures compiled by ESCAP regarding groundwater utilization by various sectors of the economy in selected countries of the region are presented in Table 1.3.

It appears that in China major thrust in groundwater development was initiated in the 1950s especially in the northern Huang-Huai-Hai plain for irrigation. Groundwater development for municipal and industrial purposes is continuing in the coastal areas.

In Bangladesh, India and Pakistan, considerable progress in groundwater development has been achieved through drilling hundreds of thousands of tube-wells for irrigation. In Malaysia, Bhutan and Lao People’s Democratic Republic, where major groundwater development programmes have not been undertaken until recently, plans for large scale development are now being seriously considered.

In the process of groundwater development and utilization, the countries of the region are confronted with several problems. In certain areas groundwater reservoirs remain unexploited while in some areas water table levels are declining due to excessive pumping. Groundwater quality problems arise in several locations due to salt water intrusion, contamination from municipal wastes and return flows from agricultural lands.

Irrigation and Irrigation Systems Management:

Irrigation is an important aspect towards contributing to increased agricultural production. Table 1.4 shows the development of irrigated areas in some of the countries in the Asia-Pacific region. At present, China and India have the world’s largest irrigated areas.

In view of the large areas under irrigation, the benefits resulting from efficient water management could be significant.

In the last two to three decades, there has been a phenomenal growth in the irrigated areas in the Asian region. In all most all the countries in the Asian region considerable number of irrigation systems have been constructed. However, the performance of these irrigation systems has come in for considerable criticism.

Among the irrigation systems, the relatively larger ones have been subjected to more criticism while the smaller ones appear to have performed well. In case of the large irrigation systems, several adverse performance parameters have been mentioned.

These include economic factors like inadequate returns on investments, performance factors like low water use efficiencies, social factors like failing to achieve equitable water distribution and finally environmental factors like soil salinization, contamination of groundwater resources and adverse public health effects.

Proper management of irrigation systems at present is an important issue. The areas which are irrigated under large irrigation projects are referred to as command areas. Before the irrigation projects came under operation, these areas were generally under rain fed agriculture.

With the introduction of irrigation facilities, these areas need to be developed systematically for irrigated agriculture. Other supporting activities like improved agricultural practices, marketing, transport, etc., help in the overall development of these command areas. Realizing the need for the development of command areas several projects for command area development have been initiated in India.

The major functions envisaged for the command area development projects are:

1. Modernization and efficient operation of irrigation systems as well as development of main drainage systems beyond the farmers block of 40 ha;

2. Construction of field channels;

3. Land shaping and land levelling;

4. Construction of field drains;

5. Lining of field channels/water courses;

6. Exploitation of groundwater through tube wells, open wells etc.

7. Adoption and enforcement of suitable cropping patterns;

8. Enforcement of a suitable rostering system of distribution of water among farmers;

9. Preparation of plan of input supply for credit, seeds, fertilizers, pesticides etc.

10. Making arrangements for timely and adequate supply of various inputs; and

11. Strengthening of existing extension, training and demonstration organizations.

Agricultural Drainage:

Application of excess water to crops, either due to rainfall or due to irrigation can harm crop production. The disposal of rain water, though on a wider scale is a flood control problem, is of serious concern to agricultural lands. Rain water not required by the crops has to be safely conveyed to the drainage system.

Generally, the problem of surface drainage exists in varying degrees in most of the irrigated areas. It is particularly serious in flat land with inadequate outfall. Constructions of roads, railways and canals have blocked the natural surface drainage in several places aggravating the drainage problem.

In some areas, either due to extensive canal irrigation or due to the geological conditions of the soil substrata, the underground water level rises to such an extent so as to affect crop growth. Such areas are said to be waterlogged. Rise of the underground water level could in some areas bring up harmful salts to the surface layers of the soil.

The Indus plain lying in India and Pakistan is an example of the drainage problems resulting from large scale irrigation. Measures are now being taken to provide both surface and subsurface drainage systems.

Watershed Management:

Watershed management involves a combination of practices which could include agricultural, forestry and engineering measures to achieve certain objectives of land and water management on a regional basis. The objectives could be flood control, water conservation or sediment reduction.

Planning for integrated soil conservation measures in the catchments of large reservoirs in order to reduce the sediment inflow into them is an example. The reservoirs constructed for irrigation and power could be silted up prematurely unless soil erosion is controlled in their catchments.

Construction of storage ponds either for flood control or for water storage for irrigation, channel improvement measures etc., come under the purview of watershed management. Planning for watershed management requires detailed information about the land use and hydrology of the area.

Aerial photographs and remote sensing techniques are useful in obtaining information for planning watershed management projects. Watershed management projects have been initiated in the catchments of several river valley projects in India with a view to reduce the sedimentation of the reservoirs.

Computer Applications:

With the availability of computers, a large number of problems in land and water management are being approached using computer applications. Computers are being used for implementing mathematical models for estimating runoff, surface irrigation system design, canal operation, design of sprinkler and trickle systems, drainage system design etc.

A large number of problems relating to groundwater and groundwater management are solved using computers. Computers are also being widely used in data base management, interpretation of remote sensing data and geographic information systems.

Geographic Information Systems (GIS) are emerging as an important and useful computerized information management tool to support resource management applications. The GIS allows resource managers to input, manage, analyze, manipulate, and display geographic data using computers.

The use of computers in the area of land and water management will certainly increase in the future, and professionals involved in land and water management need to understand these applications.

Environmental Management:

Environmental management implies utilization of natural resources without degrading their quality. In agriculture, the concern is to protect land from degradation and water resources from pollution. Use of fertilizers, insecticides and pesticides leave residues in the soil profile and they ultimately find their way either to groundwater reservoirs or other surface water bodies.

Land disposal of municipal wastes, utilizing large areas for brick manufacturing, and indiscriminate deforestation are some of the causes of degradation of land quality. As many potential agricultural pollution problems are related to soil loss and water movement, management practices that prevent erosion and make efficient use of water will minimize these hazards.

Practices that will make more efficient use of fertilizers and control the movements of pesticides in soil, water and air are needed to ensure that the residues will not become environmental contaminants.

The concept of ecological systems or ecosystems and their management is closely related to land and water. The ecosystem refers to a natural system comprising living organisms and their environment.

The concept can be applied at the level of a watershed, a pond or a wet land. Whatever the scale, the principle of the ecosystem is that all elements are intricately linked by flows of energy and nutrients, and a change in one element will have effects in the rest of the system.

Concept of Sustainable Development:

The concept of sustainability in relation to natural resources and the environment is becoming impor­tant.

The following definitions of sustainable development broadly indicate the concepts involved:

(i) Food and Agriculture Organization:

“Sustainable development is the management and conservation of the natural resource base and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for present and future generations.

Such sustainable development (in the agriculture, forestry and fisheries sectors) conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable”.

(ii) Technical Advisory Committee, Consultative Group of International Agricultural Research (CGIAR) (1988):

“Sustainable agriculture should involve the successful management of resources to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources”.

Agricultural production can only be sustained on a long-term basis if the natural resources viz., land, water and forests—upon which it is based are not degraded by inappropriate farming practices. This is true for irrigated as well as rain fed crop production systems.

Although suitable technologies have not yet been developed for all problems and situations, many of the practices contribute to a sustainable use of the land and water resources for agriculture.

Role of the Agricultural Engineer:

The agricultural engineer by virtue of his training in soils, water, crops and engineering principles is equipped to carry out the land and water management engineering programmes.

His knowledge of farm machinery, irrigation and drainage helps him in designing the water management systems in irrigated agriculture. In this area, he essentially bridges the gap between the traditional civil engineer and the agriculturist.

By controlling soil erosion in agricultural lands he helps in conserving soil fertility and at the same time helps in retarding the sediment inflow to the reservoirs wherever such areas are part of the catchments.

Through land development he helps in bringing more areas under cultivation. By designing the farm irrigation systems and agricultural drainage systems, he not only helps in better utilization of agricultural lands but also helps in maintaining the high productivity of irrigated areas.

The agricultural engineer can contribute towards the designing and maintaining aquacultures systems as they essentially contain land and water components. Thus, the agricultural engineer has a very significant role in the management of the land and water resources.