Impact on Watershed due to Land Use
Watershed and the land use are quite inter-dependent. Watersheds with a healthy aquatic system -in the form of adequate streams & wetlands, and an equally healthy biotic system -in the form of adequate flora and fauna, are generally sustainable systems. Once they are subjected to large scale human interventions and/ or natural calamities, the land use gets altered significantly. This in turn causes major impact in the watershed in terms of its hydrology, flora and fauna.
In many parts of the world, extensive areas of native forests and grasslands have been converted into croplands or urban areas or road/ railway systems/ networks. This has resulted in the alteration of riparian corridors, drainage of wetlands and modification of natural river systems. These changes in the land use have resulted in the hydrologic changes in the watersheds, their stream systems and surface water-groundwater linkages. Changes in water quantity and quality can affect people and ecosystems in both upstream and downstream areas of watersheds [Brooks et al, 2013].
If these changes occurring in watersheds are not managed properly, they may become unsustainable in the long run. Therefore to avoid any undesirable consequences, increased attention is being paid to maintaining or restoring natural stream channel systems, riparian communities, wetland ecosystems and floodplains which can restore the good hydrologic conditions of watersheds. Thinking on these lines, Hey (2001) called for a major program to maximize the natural storage in the wetlands and floodplains as well as to minimize conveyance in the upper Mississippi River Basin. Such a program would effectively reverse some of the impacts of the past 200 years of levee construction and other engineering practices in the basin.
If watersheds are not sustainably managed, they may show cumulative watershed effects i.e., combined environmental effects of activities in a watershed that can adversely impact beneficial uses of lands [Sidle, 2000]. Individually these environmental effects may not appear to be relevant. But collectively, they may become significant over time and space.
For example, the conversion of forest to crop lands in one part of a watershed can cause an increase in the water and sediment flow. Likewise, road construction and drainage can also have effects in a watershed similar to drainage of a wetland at some other location. Similarly, removal of dense shrubs to increase forage production may also increase water yield in some cases, benefit certain wildlife species and reduce fire hazards. However, the same shrub removal may be detrimental to other types of wildlife. Changes in vegetation composition/ density/ age structure/ continuity across the landscape can affect evapo-transpiration losses and thereby influence antecedent soil moisture conditions, water yields & their timings, stream flow volumes & their peaks, at different parts of watersheds. Overgrazing -which results in excess trampling in a watershed and excessive soil compaction, reduces infiltration capacity and increases surface runoff. Roads and trails possibly increase soil erosion due to the exposure to erodible soil and subsoil during their construction. This reduces infiltration and concentrates overland flow from precipitation excess which erodes the increased gradients in the side slopes of cuts and fills.
The increase in flooding due to the creation of finished impervious surfaces as well as due to the filling up of water bodies especially in the urbanized areas leading to a drastic reduction in infiltration or surface storage is very well known. On the other hand, forest and wild land watersheds are frequently affected by wild fires. This results in increased soil erosion due to the loss in the vegetation cover and also an increased surface runoff due to the formation of water repellent layers in the soil.
These are some of the examples wherein a change in land use has impacted the watersheds and made them ecologically unsustainable. There are many other examples of land use changes which also disturb the watersheds in terms of water quality, geomorphic and hydrologic effects. To overcome these undesirable effects, an interdisciplinary approach involving hydrology, geomorphology and ecology into watershed management and land use planning is needed to understand and appreciate the impacts of cumulative watershed effects on water yield, other stream flow characteristics and water quality. The next section will deal with the planning the land use so as to ensure sustainability in watershed management.
4.2 Planning the Land Use
There are conflicts over land use, many a times. The demands for arable land, grazing, forestry, wildlife, tourism and urban development are greater than the land resources available. In the developing countries, these demands become more acute every year. The population dependent on the land for food, fuel and employment is expected to double within the next 25 to 50 years. Even where land is still available in plenty, many people may have inadequate access to land or to the benefits from its use. In the face of scarcity, the degradation of farmland, forest or water resources are visible for all to see but individual land users lack the incentive or resources to stop it.
Land-use planning is the systematic assessment of land and water potential, alternatives for land use and economic and social conditions in order to select and adopt the best land-use options. Its purpose is to select and put into practice those land uses that will best meet the needs of the people while safeguarding the resources for the future. The driving forces in land use planning are the needs for change, improved management or quite different patterns of land use dictated by the changing circumstances.
All kinds of rural land use like agriculture, pastoral lands, forestry, wildlife conservation and tourism are involved in land use planning. It also provides guidance in cases of conflict between rural land use and urban or industrial expansion, by indicating which areas of land are most valuable under rural use.
The following two conditions must be met if the land use planning is to be useful:
The need for changes in land use or the action to prevent some unwanted changes which must be accepted by the people involved;
There must be the political will and ability to put the plan into effect.
Wherever these two conditions are not met and the problems are pressing, it may be appropriate to mount an awareness campaign or set up demonstration areas with the aim of creating the conditions necessary for effective planning. Our basic needs of air, water, food, clothing shelter and fuel must be met from the land which is in limited supply. As population and aspirations increase, the land becomes an increasingly scarce resource.
Land must change to meet new demands which may bring new conflicts among the competing uses of the land and among the interests of individual land users and the common good. Land taken for towns and industry is no longer available for farming. Likewise, the development of new farm land may compete with forestry, water supplies and wildlife.
Planning to make the best use of land is an established idea. Over the years, farmers have made plans season after season, deciding what to grow and where to grow it. Their decisions have been made according to their own needs, knowledge of the land & the technology, labour and capital available. As the size of the area, the number of people involved and the complexity of the problems increase, the need for information and rigorous methods of analysis and planning also increase.
However, land-use planning is not just farm planning on a different scale. It has a further dimension, namely the interest of the whole community. Planning involves anticipation of the need for change as well as reactions to it. Its objectives are set by social or political requirements which take into account of the existing situation. In many places, the existing situation cannot continue because the land itself is being degraded. Examples of unwise land use include the following:
(a) The clearance of forest on steep lands or on poor soils for which sustainable systems of farming have not been developed so far
(b) Overgrazing of pastures
(c) Industrial, agricultural and urban activities that produce pollution.
Degradation of land resources may be attributed to human greed, ignorance, uncertainty or lack of an alternative but essentially, it is a consequence of using land today without investing in tomorrow. Land-use planning aims to make the best use of limited resources by the following actions:
Assess the present, future needs and systematically evaluating the land's ability to supply them;
Identify and resolve the conflicts among competing uses, the needs of individuals and those of the community, and among the needs of the present generation and those of future generations;
Seek sustainable options and choose those which fully meet identified needs;
Plan to bring about desired changes; and,
Learn from experience.
There can’t be a blueprint for change. The whole process of planning is iterative and continuous. At every stage, as better information is obtained, a plan may have to be changed to take account of it.
i) Goals of Land Use Planning
Goals of land use planning define what is meant by the "best" use of the land. They should be specified at the outset of a particular land use planning project. Goals may be grouped under the following three headings of efficiency, equity & acceptability and sustainability.
Efficiency: Land use planned must be economically viable. Therefore, one goal of development planning is to make an efficient and productive use of the land. For any particular land use, certain areas are better suited than others. Efficiency is achieved by matching different land uses with the areas that will yield the greatest benefits at the least cost, i.e., maximum benefit cost ratio.
Efficiency might mean different things to different people. To the individual land user, it means the greatest return on capital and labour invested or the greatest benefit from the land area available. Government objectives are more complex: they may include improving the foreign exchange situation by producing for export or for import substitution.
Equity & Acceptability: Land use must be socially acceptable. It should ensure food security, employment and income security in rural areas. Land improvements and redistribution of land may be undertaken to reduce inequality or to attack absolute poverty. One way of doing this is to set a threshold standard of living to which the target groups should be raised. Living standards may include levels of income, nutrition, food security and housing. Planning to achieve these standards involves the allocation of land for specific uses as well as the allocation of financial and other resources.
An example of acceptability is given here. Following the drought of 1973-74 and the subsequent famine, the Government of Ethiopia became more aware of the serious degradation of soil in the highlands.
An ambitious soil conservation programme which concentrated on protecting steep slopes by bunding and afforestation was launched. This had made a substantial impact on soil erosion but has not contributed much to in increasing agricultural production. Large-scale afforestation was also unpopular with local people because it reduced the area available for livestock grazing while forest protection implied denying access to the public for fuel wood collection. A balance between the competing requirements of conservation and production was clearly needed if popular support for soil conservation work was to continue without inducements such as the Food-for-Work Programme.
A land-use plan to conserve steeper slopes by restoring good vegetative cover through closure, followed by controlled grazing, was found to be more acceptable to the local people than large-scale afforestation applied in isolation.
Sustainability: Sustainable land use is that which meets the needs of the present while simultaneously conserving resources for future generations. This requires a combination of production and conservation. The production of the goods required by the people now need to be combined with the conservation of natural resources on which that production depends so as to ensure a continued production in the future.
A community that destroys its land will forfeit its future. Land use has to be planned for the community as a whole because the conservation of soil, water and other land resources is often beyond the means of individual land users.
ii) Trade-offs among Conflicting Goals of Land Use Planning
Clearly, there are conflicts between these various goals of land use planning. More equity may lead to less efficiency. In the short term, it may not be possible to meet the needs of the present without consuming resources such as burning oil or clearing areas of natural forest. Decision-makers need to consider the trade-offs between different goals. But if the system as a whole is to survive, the use of natural assets must be compensated by the development of human or physical assets of equal or greater worth.
Good information such as information about the needs of the people, about land resources and about the economic, social and environmental consequences of alternative decisions is always essential. The job of the land use planner is to ensure that decisions are made on the basis of consensus or acceptable degree of disagreement.
In many cases, planning the processes like introducing appropriate new technology can reduce the costs in trade-off. It can also help in resolving the conflict by involving the community in the planning process and by revealing the rationale and information on which decisions are based.
iii) The Focus of Land Use Planning
The following points constitute the focus of land use planning.
Land Use Planning is for the People: People's needs are the driving forces in the land use planning process. Local farmers, other land users and the wider community who depend on land must accept the need for a change in land use, as they will have to live with its results.
Land use planning must be positive and needs to be for the people’s betterment. The planning team must find out about people's needs and also about the local knowledge, skills, labour and capital that they can contribute. It must study the problems of existing land use practices and seek alternatives while drawing the public attention to the hazards or inconveniences of continuing with the present practices and to the opportunities for change.
Regulations to prevent people doing what they now do for pressing reasons are most likely to fail. Local acceptability is readily achieved by local participation in land use planning. The support of local leaders is essential. At the same time, the participation of agencies that have the resources to implement the plan is also important.
Land is not the Same Everywhere: Land is the other focus of land-use planning. Capital, labour, management skills and technology can be moved to where they are needed. On the other hand, land cannot be moved, and different areas present different opportunities and different management problems. The land resources are generally changing as it is obvious in the case of climate and vegetation. But the examples such as the depletion of water resources or the loss of soil by erosion or salinity remind us that resources can be degraded, many a times irreversibly. Good information about land resources is thus essential to land use planning.
Technology: A third element in land use planning is the knowledge of technologies like agronomy, silviculture, livestock husbandry and other means by which land is used. The technologies recommended must be appropriate technologies for which the users have the capital, skills and other necessary resources. New technologies may have social and environmental implications that should be addressed by the land use planner(s).
Integration: A mistake in early attempts at land use planning was to focus too narrowly on land resources without enough thought given to their possible use. Good agricultural land is usually also suitable for other competing uses. Land use decisions are not made only on the basis of land suitability but also according to the demand for products and the extent to which the use of a particular area is critical for a particular purpose. Planning has to integrate information about the suitability of the land, the demands for alternative products or uses and also the opportunities for satisfying those demands on the available land, now as well as in the future.
Hence, land use planning is not sectoral. Even where a particular plan is focused on one sector, e.g., small holder tea development or irrigation, an integrated approach has to be carried down starting from the strategic planning at the national level to the details of the individual projects and programs at district and local levels.
iv) Land Use Planning at Different Levels
Land use planning can be applied at three broad levels: national, district and local. These are not necessarily in that order. They correspond to the levels of government at which decisions about land use are taken.
Different kinds of decisions are taken at each level, where the planning methods and plan types also differ. However at each level there is a need for a land use strategy, policies that indicate planning priorities, projects that tackle these priorities and operational planning to get the work done smoothly, swiftly and cost-effectively.
The greater the interaction between the three levels of planning, the better for all. The flow of information should be in both directions. At each successive level of planning, the degree of details needed as well as the direct participation of the local people increase.
National Level Land Use Planning: At the national level, land use planning is concerned with the national goals and the allocation of resources. In many cases, national land use planning may not involve the actual allocation of land for different uses. In place of them, it may establish the priorities for district level projects. A national land use plan may cover:
1. Land-Use Policy related to balancing the competing demands for land among different sectors of the economy such as food production, export crops, tourism, wildlife conservation, housing & public amenities, roads, industry;
2. National Development Plans and Budget consisting of project identification and the allocation of resources for development;
3. Coordination of sectoral agencies involved in land use;
4. Legislation on such subjects as land tenure, forest clearance and water rights.
National goals are complex while policy decisions, legislation and fiscal measures affect a large population and wide areas. Decision makers can’t possibly be specialists in all facets of land use. So the planners' responsibility is to present the relevant information so that the decision makers can both understand and act on it.
District Level Land Use Planning: District level refers not necessarily to administrative districts but also to land areas that fall between national and local levels. Development projects are generally at this level, where planning first comes to the grips with the diversity of the land and its suitability to meet the project goals. When planning is initiated nationally, national priorities need to be translated into local plans. Conflicts between national and local interests should be resolved. The kinds of issues tackled at this stage include:
1) The siting of developments such as new settlements, forest plantations, irrigation schemes, etc.;
2) The need for improved infrastructure such as water supply, roads, marketing facilities, etc.;
3) The development of management guidelines for improved types of land use on each type of land.
Local Level Land Use Planning: The local planning unit may be the village, a group of villages or a small watershed or a catchment. At this level, it is very easy to fit the plan to the people, making use of local people's knowledge and contributions. Wherever the planning is initiated at the district level, the programme of work to implement changes in land use or management has to be carried out locally. Alternatively, this may be the first level of planning, with its priorities drawn up by the local people. Local level planning is about getting things done on particular areas of land including what shall be done where and when, and who will be responsible.
Some of the examples of local level land use planning are:
1) Layout of drainage, irrigation and soil conservation works;
2) Design of infrastructure - road alignment and the siting of crop marketing, fertilizer distribution, milk collection or veterinary facilities;
3) Siting of specific crops on suitable land.
Requests at the local level, e.g., for suitable areas to introduce tobacco or coffee, must be met with firm recommendations. Planning at these different levels needs information at different scales and levels of generalization. Much of this information may be available in maps. The most suitable map scale for national level land use planning is one by which the whole country fits on to one map sheet, which may call for a scale ranging from 1:5 million to 1:1 million or larger. District level land use planning requires details to be mapped at about 1:50000, although some information may be summarized at smaller scales ranging to 1:250000.
For local level land use planning, maps in the scales ranging between 1:20000 and 1:5000 are found to be the best. Reproductions of air photographs can be used as base maps at the local level land use planning, since field workers and experience can show that local people can recognize where they are on the photos.
v) Land Use in Relation to Sectoral and Development Planning
Land use planning is non-sectoral by definition but, unless a special planning authority is set up, a land use plan must be implemented by sectoral agencies - in agriculture, forestry, irrigation, etc. Implementation will call for help from the different extension services.
There will be no clear boundary between land use planning and other aspects of rural development. For example, a desirable change in land use may be the introduction of a cash crop. Successful management may require the use of fertilizers. This cannot be done unless there are local centres for fertilizer distribution, effective advice on its use and a system of credit for its purchase.
Local services will be of no use without an adequate national distribution system and the sufficient manufacture or allocation of foreign currency for imports. Building a fertilizer factory and organizing national distribution are definitely not part of land use planning but they may be essential for the success of planned land use. On the other hand, the siting of local distribution centres in relation to population and suitable land could well be part of the work of a land use planner.
Hence, there is a spectrum of activities ranging from focus on the interpretation of the physical qualities of the land for which the land use planner will be largely responsible to activities that need a combined input with other technical specialists. Furthermore, where matters of national policy such as adequate prices for crops are prerequisites for successful land use, the job of the planner(s) is to mention it clearly.
vi) People Involved in Land Use Planning
Land use planning involves getting many different people to work together towards common goals. The following three groups of people are directly involved:
Land Users: These are the people living in the planning area whose livelihood depends wholly or partly on the land. They include not only the farmers, herders, foresters and others who use the land directly but also those who depend on these people's products such as operators in crop or meat processing, sawmills and furniture factories. The involvement of all land users in planning is very essential. Ultimately, they have to put the plan into practice and must therefore believe in its potential benefits as well as in the fairness of the planning process.
The experience and determination of local people in dealing with their environment are generally the most neglected in spite of being the most important resource. People will grasp development opportunities that they themselves have helped to plan more readily than any other schemes that are imposed on them. Without the support of local leaders, a plan is not likely to succeed.
Achieving effective public participation in planning is a real challenge. Planners have to invest the time and resources needed to secure participation through local discussions, by broadcasting and newspaper articles, through technical workshops and extension services. Imagination, a sincere interest in people and the land as well as a willingness to experiment mark the more successful efforts by the land users.
Decision Makers: Decision makers are those responsible for putting plans into effect. At the national and district levels, they will usually be government ministers. At the local level, they will be members of the local self-government or other authorities.
Generally, the planning team provides information and expert advice. The decision makers guide the planning team on key issues and goals while also deciding whether to implement plans and if so, which of the options presented need to be chosen. Although the leader of the planning team is in charge of the day-to-day planning activities, the decision maker(s) should be involved at regular intervals. Decision makers also have a key role in encouraging public participation through their willingness to expose their decisions and the way they are reached to public scrutiny.
Land Use Planning Team: An essential feature of land use planning is the treatment of land and land use as a whole. This involves crossing boundaries between disciplines like natural resources, engineering, agriculture and social sciences. Therefore teamwork is essential. Ideally a team needs a wide range of special expertise such as a soil surveyor, a land evaluation specialist, an agronomist, a forester, a range and livestock specialist, an engineer, an economist and a sociologist.
Such a range may be available only at the national level. At the local level, a more typical planning team may consist of a land use planner and one or two assistants. Each member must tackle a wide range of jobs and will subsequently need specialist advice. Government agency staff and universities may be useful sources of such advice or assistance.
Applications of Remote Sensing and Geographical Information System (GIS) in Watershed Planning
Remote sensing and GIS two of the important modern tools which have many applications in watershed planning. In this section, the remote sensing applications in watershed planning are discussed followed by the GIS applications.
Doppler RADAR (i.e., Radio Amplification Detection and Ranging) is used in the enhanced meteorological collection of data such as wind speed and direction within weather systems. By measuring the bulges of water caused by gravity, features on the seafloor to a resolution of about a mile are mapped. By measuring the height and wavelength of ocean waves, the altimeters measure wind speeds and direction and surface ocean currents and directions. Light detection and ranging (LIDAR) is used to detect and measure the concentration of various chemicals in the atmosphere, while airborne Heights of objects and features on the ground can be measured more accurately by LIDAR than radar technology.
Remote sensing of vegetation cover is a principal application of LIDAR. Simultaneous multispectral platforms such as the images from the Landsat remote sensing satellite have been in use since the 1970s. Maps of land cover and land use from thematic mapping can be used to find minerals, detect or monitor land usage and deforestation and examine the health of indigenous plants and crops, including entire farming regions or forests.
Within the scope of the combat against desertification, remote sensing allows to follow up and monitor risk areas in the long term, to determine desertification factors, to support decision-makers in defining the relevant measures of environmental management and to assess their impact on watershed planning. After the successful launching of India’s remote sensing satellites viz., Bhaskara 1 and Bhaskara 2 in 1979 and 1981, respectively, India began developing an indigenous Indian Remote Sensing (IRS) satellite program to support the national economy in the areas of agriculture, water resources, forestry and ecology, geology, watersheds, marine fisheries and coastal management.
The Indian Remote Sensing satellites are the mainstay of National Natural Resources Management System (NNRMS) for which Government of India’s (GoI) Department of Space (DOS) is the nodal agency, providing operational remote sensing data services. Data from the IRS satellites are received and disseminated. With the advent of high-resolution satellites, new applications in the areas of urban sprawl, infrastructure planning and other large-scale applications for mapping have been initiated. Remote sensing applications in the country, under the umbrella of NNRMS, now cover diverse fields within the domain of watershed planning and management such as pre-harvest crop area and production estimation of major crops, drought monitoring and assessment based on vegetation condition, flood risk zone mapping etc.
GIS has been widely used in characterization and assessment studies which require a watershed-based approach. Basic physical characteristics of a watershed such as the drainage network and flow paths can be derived from readily available Digital Elevation Models (DEMs) and data such as the United States Geological Survey’s (USGS) National Hydrography Dataset (NHD) Program. This, in conjunction with precipitation and other water quality monitoring data from sources such as the Environmental Protection Agency’s (EPA) BASINS (i.e., Better Assessment Science Integrating Point & Non-point Sources) database and USGS, enhances development of a watershed action plan and identification of existing and potential pollution problems in the watershed.
Data gathered from Global Positioning System (GPS) surveys and from environmental remote sensing systems can be fused within a GIS for a successful characterization and assessment of watershed functions and conditions.
● Management Planning
When faced with challenges involving water quality and quantity due to natural as well as human-induced hazards (e.g., droughts, hazardous material spills, floods, and urbanization), planning becomes extremely important so as to mitigate their impacts and ensure optimal utilization of the available resources. Information obtained from characterization and assessment studies, primarily in the form of charts and maps, can be combined with other datasets to improve understanding of the complex relationships between natural and human systems as they relate to land and resource use within watersheds. GIS provides a common framework [i.e., spatial location] for watershed management data obtained from a variety of sources. Because watershed data and watershed biophysical processes have spatial dimensions, GIS can be a powerful tool for understanding these processes and for managing potential impacts of human activities.
The modeling and visualization capabilities of modern GIS, coupled with the explosive growth of the Internet and the World Wide Web, offer fundamentally new tools to understand the processes and dynamics that shape the physical, biological and chemical environment of watersheds. The linkage between GIS, the Internet, and environmental databases is especially helpful in planning studies where information exchange and feedback on a timely basis is very crucial and more so when there are several different agencies and stakeholders involved.
● Watershed Restoration (Analysis of Alternative Management Strategies)
Watershed restoration studies generally involve evaluation of various alternatives and GIS provides the perfect environment to accomplish that efficiently and accurately. GIS has been used for restoration studies ranging from relatively small rural watersheds to heavily urbanized landscapes. Coupled with hydrodynamic and spatially explicit hydrologic/water quality modeling, GIS can assist in unified source water assessment programs including the total maximum daily load (TMDL) program. As an example, alternatives for restoring a waterbody or a watershed can be studied by creating digital maps that show existing conditions and comparing them to maps that represent the alternative scenarios. GIS can also provide a platform for collaboration among researchers, watershed stakeholders, and policy makers, significantly improving consensus building and offering the opportunity for collaborative work on interdisciplinary environmental policy questions. The integrating capabilities of a GIS provide an interface to translate and emulate the complexities of a real world system within the confines of a digital world accurately and efficiently.
● Watershed Policy Analysis and Decision Support
The field of watershed science, particularly watershed planning, is experiencing fundamental changes that are having profound impact on the use of computer-based simulation models in resource planning and management. On one hand, the dramatically increased availability of powerful, low-cost, and easy-to-use GIS software, and more extensive spatially referenced data, are making GIS an essential tool for watershed planning and management tasks. However, with this increased use has come an increased realization that GIS alone cannot serve all the needs of planning and managing watersheds. This realization has renewed resource planners’ interest in development of decision support systems that combine GIS, spatial and non-spatial data, computer-based biophysical models, knowledge-based (i.e., expert) systems, and advanced visualization techniques into integrated systems to support planning and policy analysis functions. As a component of a spatial decision support system, GIS provides very powerful visualization facilities for display and manipulation, giving immediate intuitive evaluation capabilities to which a wide range of non-technical users and decision makers can relate to.
GIS can assist the decision maker in dealing with complex management and planning problems within a watershed, providing geo-processing functions and flexible problem- solving environments to support the decision research process.
A casual look at the environmental/ecological science literature reveals intense research activities in GIS-based watershed management and planning. The explosive growth in the use of GIS for the activities listed above is testimony to its rapid evolution into a complex array of applications and implementations.
Keywords: Land use, impact on watershed, land use planning, land use goals, land use trade-offs.