Project Report on Watershed Management

A project report on Watershed Management. This report will help you to learn about:- 1. Concept of Watershed Management 2. Objectives of Watershed Management 3. Planning 4. Measures 5. Land use Planning 6. Flood Control and Watershed Management 7. Socio-Economic Aspects 8. Recent Trends in Watershed Management Research.

Contents:

1. Project Report on the Concept of Watershed Management
2. Project Report on the Objectives of Watershed Management
3. Project Report on the Planning Watershed Management
4. Project Report on the Measures for Watershed Management
5. Project Report on the Land use Planning for Watershed Management
6. Project Report on the Flood Control and Watershed Management
7. Project Report on the Socio-Economic Aspects of Watershed Management
8. Project Report on the Recent Trends in Watershed Management Research

Project Report # 1. Concept of Watershed Management:

A watershed is a drainage area on earth’s surface from which runoff, resulting from precipitation flows past a single point into a larger stream, a river, a lake or the ocean. Many definitions have been developed over the recent years for the term watershed. While the definitions employ a wide variety of words, they all mean practically the same thing.

Most generally, a watershed can be defined as a body of soil with definite boundaries around it, above it, and below it. In other words, it is a land surface (body of soil) bounded by a divide which contributes runoff to a common point. A positive water accretion to its upper boundary is in the form of precipitation and a negative accretion is in the form of evaporation.

There can be drainage laterally or vertically, when water runs out of it, and leakage, when there is a perched water horizon. Generally water­shed and drainage basin are used synonymously. In British literature, catch­ment is used for a drainage area. From the hydraulic point of view, a drainage basin can be defined as the soil surface from which water flows into a certain outlet or collector.

Watershed management involves management of the land surface and vegetation so as to conserve and utilise the water that falls on the watershed, and to conserve the soil for immediate and long-term benefits to the farmer, his community and society. As such, watershed management is not new to India.

Since centuries, India has developed and used tanks and ponds (Fig. 11.1) on an extensive scale to harvest water from watersheds, store and recycle it for crop use. People were also aware of the problem of sedimentation of these tanks as evidenced by desilting operations carried out from time to time.

Prac­tices such as bunding and other cultural operations to conserve moisture are prevalent on dry lands, since long. Watersheds may be only a few acres or hundreds of thousand square kilometres such as watershed at the mouth of Ganges. All watersheds can be divided into smaller and smaller sub-water­sheds.

There is ample evidence to show that proper use of watershed lands has a lot to do with the quantum and quality of runoff from the watershed, ground water supply, flood effects and other hydrologic factors.

Soil conservation work on individual farms largely benefits these properties, but it is considered that greater benefits would accrue if the programme is carried out taking watersheds as units of management so as to achieve the greatest possible im­provement in the control of water and sediment.

Watershed conservation or management is not something to take the place of soil conservation district programmes or farm improvement programmes. It is, in fact, the regular programme of farm, district or state, supplemented by addition of flood prevention and other measures on small tributaries and by wider participation of whole community.

It is a soil conservation programme, extended to meet some of the community type land and water problems, for which the districts or other local interests do not have the facilities to handle.

As a natural unit, watershed reflects the interaction of soil, geology, water and vegetation by providing a common end product runoff or stream flow whereby the net effects of these interactions on that product can be measured and ap­praised.

A watershed is made up of number of individual community components, processes and physical, economical and social ingredients. Watershed is the land from which water flows into stream, lake or other point of drainage. But its geography is only one component of the watershed for the purpose of watershed programmes.

Other watershed elements include, for example, the timber or grass growing on the watershed and the land in cultivation. They include land use, conditions of erosion and soil depletion, soil fertility and productiveness, and the people with their community interests. All these factors have to be taken into account in their proper relationships for effective watershed planning and treatment.

Conservation on one farm must also be related to that on the other farms, and in turn the effect of the Conservation measures on both the rural and the urban property and facilities must be considered. This calls for working out sys­tematic use of water from the top of each watershed to the bottom.

Project Report # 2. Objectives of Watershed Management:

Watershed management implies the wise use of all soil and water resources, so as to provide a clean, uniform water supply for beneficial use and to control damaging overflow. The term is very nearly synonymous with soil and water conservation with the difference that the emphasis is given on flood protection and sediment control also besides maximising crop production.

The basic ob­jective of watershed management is thus to meet the problems of land and water use not in terms of any one resource but on the basis that all the resources are interdependent and must, therefore, be considered together.

The water­shed aims, ultimately, at improving standard of living of common man in the basin by increasing his earning capacity, by offering facilities such as electricity, water for irrigation, and drinking water supply, freedom from fears of floods and droughts, etc.

The overall objectives of watershed development program­mes may be outlined as below:

(1) Recognition of watersheds as a proper unit for wise utilisation and development of all lands. The land should be treated in accordance with its peculiar need and by methods that will control soil erosion, conserve water, encourage wildlife, improve farm income and prevent flood damage to agricultural lands.

(2) Retardation and prevention of floods through small multipurpose reservoirs and other water impounding structures at the head water of streams and in problem areas.

(3) Provision for an abundant water supply for domestic, industrial and agricultural needs.

(4) Abatement of organic, inorganic and soil pollution.

(5) Broad expansion of recreational facilities, i.e. picnic and camping sites with more lakes and streams suitable for boating, fishing or swimming.

(6) Utilisation of natural local resources for improving agriculture and allied occupation or industries (small and cottage industries) so as to improve socio-economic conditions of the local residents.

Project Report # 3. Planning Watershed Management:

Social and hydrologic factors are perhaps the most important since the ele­ments involved in it, largely determine as to whether the desired programme can be carried out or not.

The portion of the hydrologic cycle from the time the water is received on the land surface until it leaves the area as stream flow, or is returned to the atmosphere by evapotranspiration process, is the central core of control in watershed management.

When precipitation strikes the surface, a number of climatic factors have varying degrees of effect upon the direction of movement of water. These are intensity, duration and type of precipitation, air temperature, wind velocity and humidity.

Hydrological characters of soil, such as infiltration capacity, moisture con­tent, and other soil characters, e.g. presence of permeable layer, substratum, texture, etc. affect the movement of water in the soil. Similarly, runoff is af­fected by the length and steepness of slope, amount and type of vegetation, stoniness, etc.

Although all these factors affecting water movement cannot be changed through management, yet some of the factors can be modified to achieve the aims of management. Soil characters can be changed by mechani­cal means.

The effectiveness length and steepness of slope can be considerably changed by agronomic and mechanical practices. Following discussion should be useful in preparing a sound watershed management plan.

A. Inter-Disciplinary Team Work in Watershed Management Planning:

Watershed planning is a coordinated analysis by a team of technicians repre­senting various disciplines. The principal disciplines are hydrology, geology, engineering, soil science, agronomy and economics.

However, there is no divid­ing line between their areas of responsibility. Each discipline is dependent on, and inter-related with, each other. Preparation of a work plan requires the input of considerable effort by various technicians, scientists and economists.

B. Size of the Manageable Watershed:

The evident question of how big the watershed could be for planning can be solved by past experience and national guidelines. The size can be adjusted depending upon the problem involved.

In gully control and drainage problem areas the watershed units may be smaller than in flood problem areas. Where floods are foremost problems, several smaller units may be combined until upstream problem areas are included within the watershed areas.

C. Demarcation of Priority Watersheds on the Basis of Vulnerability of Erosion:

A big watershed may be divided into several smaller viable sized sub-water­sheds. The watersheds may be given priority ratings on the basis of erosion indices and delivery ratios for locating highly vulnerable mini-watersheds or sub-watersheds. The high priority rated sub-watersheds require prime attention.

D. Preliminary Data for Management Planning:

Principal factors, that affect the operation of individual watersheds, and which must be studied before management plan could be developed are: shape of the watershed, topography and slope of the land, soils and their characteristics, amount of precipitation and storm patterns, land use and cropping pattern on watershed, and size of the watershed.

Necessary data for interpretation include:

(1) Meteorological;

(2) Hydrological;

(3) Soil and land use and soil water conditions; and

(4) Economic and so­cial.

(5) Summary of Management Plan

A preliminary investigation and collection of data requires a detailed reconnaissance of the watersheds, utilizing available maps and aerial photographs. Damaged and more vulnerable areas may be located and damageable values estimated.

Soil and land capability maps should be prepared to assist in land use and crop management planning. It is necessary to identify the potential structural sites and key sites. For a sound work plan, the basic data collected should be analysed with objective interpretations. A brief account of the purpose for which meteorological, hydrological, soil and land use data are needed is given below.

(1) Meteorological Information:

Precipitation data are used in watershed planning to estimate the frequency and magnitude of floods and dependability of water supplies in watersheds. It is especially valuable for hydrologists as a basis for extrapolating stream flow.

The data should give the measurement of annual precipitation, its seasonal dis­tribution and characters of typical storms like intensity of rainfall and frequen­cy of storm, delivering various amounts of water. Knowledge of climate is also important in growing crops.

(2) Hydrological Information:

The amount and rate of stream flow are expressed in stream flow hydrographs which represent the rate of (low past a stream gauging station over a period of time.

Four factors affect the volume and rate of runoff and consequently the shape of hydrograph:

(i) Precipitation (kind, amount, intensity and distribu­tion);

(ii) Drainage basin characteristics (size, shape, length steepness of water­shed and stream);

(iii) Soil and its plant cover; and

(iv) Changes in soil through land use.

The shape of hydrograph for each component of stream flow reflects time for water to reach the channel.

Sedimentation data is needed in watershed planning for estimation of downstream damage to deposition of sediments in reservoirs and on flood plains; for design of reservoirs and other structural works for study of channel aggradation and degradation for determining suitability of water, etc.

(3) Soil and Land Use Data:

Soil survey is essential for adequate planning. The information required from survey reports is basic for planning and improvement activities such as crop management, pasture regeneration, agronomic and mechanical measures of soil erosion control. It provides most of the information for determination of the erosion situation and delineation of major silt producing areas.

(4) Economic and Social Data:

Economic conditions of the people and its source and social customs must be known for successful watershed planning. A successful watershed protection programme requires the people, residing in the watershed, to take over the principal responsibility.

This necessitates the sponsorship of a soil conserva­tion district together with other responsible local organisations that are repre­sentatives of the interests involved and that can help in formulating and achieving the best possible programme for watershed management. It is also necessary to identify whether local interests can share a part of the cost in­volved in management work.

(5) Summary of Management Plan:

Watershed work plan should be tailored to tell the needs of the watershed and objectives of the management. The individual responsibilities of each depart­ment should be completely itemized in plan.

The plan should contain the fol­lowing minimum details:

(a) Description of the Watershed:

(i) Physical data.

(ii) Economic data.

(b) Watershed Problems:

(i) Flood water damage.

(ii) Sediment damage.

(iii) Erosion damage.

(iv) Problems related to soil and water management.

(v) Problems related to crop management.

(c) Works of Improvement to be Installed:

(i) Land treatment measure.

(ii) Structural measures.

(iii) Crop management measures.

(d) Comparison of Benefits and Costs  

Project Report # 4. Measures for Watershed Management:

Measures contributing to watershed management can be classified into two broad categories: in terms of purpose, method and accomplishments. In terms of purpose, includes land use and treatment measures which are effective in increasing the infiltration rate and water holding capacity of the soil and preventing soil erosion on watershed lands.

They include all biological and mechanical methods of erosion control, including water stabilisation measures, such as gully control by structures or vegetation. The second category of measures includes those planted primarily for the manage­ment of water-flow after it has left the fields and farm waterways and reached the small branches and cracks.

These measures include flood-water retarding structures, stream-channel improvements to increase carrying capacity and stabilise beds and banks, minor flood ways, sediment detention on basins and similar measures.

The distinguishing characteristic of this group is that their primary benefits are off-site or downstream, not at the place they are installed. In this sense the primary benefits are public, because they accrue to the other farms, towns, and roads down-streams from where the measures are installed.

The aim in efficient management should be selection of measures that could fit into the requirements of proper watershed management.

Project Report # 5. Land use Planning for Watershed Management:

The integrated land use planning for watershed management, in the limited sense, aims at comprehensive development of whole of the watershed in ac­cordance with its potentialities and capabilities for different land uses.

In the broader perspective such a planning deals with total development of all kinds of resources of the watershed, namely: land; water; climate; plant; animals; and man. The ultimate aim is to improve the economic status of the inhabitants of the watershed.

Watersheds are quite complex in their characteristics and are rarely identi­cal. Their response to development depends upon the nature of resource avail­able within their boundaries.

Therefore, a selectivity approach is more rational in choosing more responsive watersheds for a particular programme. Specific criteria and survey techniques need to be developed for selection of priority and responsive watersheds for each individual programme.

The basic criterion for selection of watersheds may be:

(i) Intensity of the problem;

(ii) Prospects of correcting the problem;

(iii) Potential for overall development;

(iv) Availability of technology;

(v) Likely acceptability and participation by the in­habitants; and

(vi) The infrastructural availability.

In order to plan developmental activities on watershed basis, a suitable framework of watersheds based upon some standard and uniform system of delineation and codification is necessary. Such a system has been developed by the All India Soil and Land Use Survey Organisation. At macro-level, it follows a 5-stage sub-division using drainage map of 1 : 1 million scale.

At micro-level, useful for operational level, watersheds of 1000-5000 ha, a 3 to 4 stage sub-division is followed using 1 : 50,000 scale drainage maps. For farm level planning and designing of different components of the programme and their implementation, base maps of 1 : 15,000 and larger scale like cadastral maps can be used.

For specific purposes, however, ad-hoc selection of small watersheds can also be made. For successful land use planning it is essential to identify problems, needs, potential, gaps, constraints, approach and implementation details and modalities.

In attempting to collect the information’s regarding important watershed characteristics, Table 11.1 can be used as a guide. However, the ten characteristics of the watershed such as size, shape, relief, drainage, geology, soils, climate, surface conditions and land use, ground water and geographic location, socio- and legal-status listed in the table are not exhaustive enough.

Once the problem is identified and objectives are defined, the priorities for a type of work in the watershed can be fixed. For example, in the catchment of a reservoir, an area yielding maximum silt load must be taken up first under the management programme. Similarly, in flood affected regions, areas contribut­ing maximum runoff need to be determined and taken under the development programme.

In the drought prone areas, it is important to determine the potentiality of different locations for possibility of maximum water harvesting and demarcating the land based on its capability for forest, pasture and agricul­ture.

The command areas need to be specified with cropping systems and response to irrigations. In salt affected soils, the reclamation programmes should be taken with priority. Similarly, areas affected with shifting cultivation and ravines need priority in order to prevent their further development.

Project Report # 6. Flood Control and Watershed Management:

A creek or river is in flood stage when its water flows over the banks and covers the bottom land. This bottom land is called ‘flood plain’ and its soil material, ‘alluvium’. In watershed management, we are more concerned with headwater flood control which includes all measures that will reduce flood flow in water­sheds of small rivers and their tributaries.

The maximum size of watershed for a headwater area is arbitrarily selected as 1500 km². Headwater flood control measures are considerably different than downstream measures. Headwater floods are typically flash floods of short duration which occur rather frequently that is, two or more times a year.

Floods cause several types of losses which can be categorized into following 3 groups:

(1) Direct Losses:

These include loss of property, crops, and land which can be determined in monetary values.

(2) Indirect Losses:

Indirect losses are depreciated property, traffic delays, and loss of income.

(3) Intangible Losses:

These include losses which are not subject to monetary evaluation, such as the community insecurity, health hazards and loss of life.

The damage to land is often unnoticed and, therefore, not recorded in terms of its monetary value. However, soil erosion from uplands, sedimentation in reservoirs, stream channels and flood plains, and pollution of water supplies greatly affects the economy of the entire watershed.

The distinction between normal discharge from a watershed and flood flow is generally determined by the stage of the stream when bankful. Most floods occur on the flood plains adjacent to rivers and streams and result from such natural causes as excessive rainfall and melting snow.

Occasionally, tidal waves or hurricanes also cause flood. Floods may also occur due to reservoir failures. Such floods are often highly life damaging but fortunately these seldom occur.

Depending upon their nature, floods are divided into two categories:

(1) Large area floods, which occur from storms of low intensity having a dura­tion of few days to several weeks; and

(2) Small area floods, which occur from storms of high intensity having a duration of one-day or less.

It has been ob­served that 85% floods fall under second category. Such floods cause great damage to agricultural land through soil erosion, which in turn results in sedi­ment accumulation in river, and reservoirs. These floods usually do not produce high runoff on large streams but often cause serious local damage.

The large area floods, on the other hand, cause greatest damage to metropolitan areas in addition to considerable agricultural losses. Flood flows are predicted from stream flow records, developed hydrographs, empirical equations, meteorological data and previous high water marks.

A. Watershed Flood Control Measures:

Broadly, watershed flood control measures can be grouped into two general classes:

(1) Those that retard flow or reduce runoff by watershed treatments, flood control reservoirs or underground storage;

(2) Those that increase the channel capacity to accelerate the flow. These include channel improvement, channel straightening and levees.

Measures that retard the flow or reduce runoff are economically and physically more desirable due to the following reasons:

(1) They remove all visible evidences or danger of flood.

(2) They result in uniform flow in the streams thereby greater recharge of the groundwater and more adequate water supply.

(3) They are the important step in the conservation of natural resources.

(4) They result higher crop yields, especially in areas with deficient ir­rigation water supply.

(5) These measures also result in reduction of sedimentation in lower tributaries.

Watershed Treatment:

Here, the objective is to increase the storage of water on the surface and in the soil profile. Watershed treatments, therefore, include all practices ap­plied to the land that are effective in reducing flood runoff, controlling erosion, and increasing the amount of surface storage, rate of infiltration and water holding capacity of the soil.

The latter three effects are related to the soil type. Runoff retardation by land management and soil type are largely dependent on vegetative cover and favourable soil surface condi­tions. As shown in Fig. 11.3, the soil type affects runoff as much as 3 times when compared between permeable and heavy soils. Similar is the case with type and density of vegetation. (Fig. 11.4).

Conservation practices, such as contouring, strip cropping and terracing will reduce flood peaks as well as total runoff from small to medium storms during the growing season. For longer storms, the effect of contouring and strip crop­ping on runoff is usually much less than the reduction in soil loss. Level or absorptive-type terraces can have a considerable effect on flood peaks of rather large watersheds.

A study conducted in the Sukhna lake having a catchment of 40 km² showed an annual average loss of 150 tonnes of sediment per hectare of the catchment. As much as 50% of the total rainfall was lost as runoff from the untreated hilly catchment.

However, package of conservation practices including construction of staggered contour trenches, check dams and planting supplemented by a debris basin have reduced sediment from 80.5 tonnes/ha/year to 3.0 tonnes/ha/year from a hilly watershed of 20 ha within a period of 11 years.

The average runoff from the catchment has come down to 10% of rainfall with 66% reduction in peak discharge within 15 years. Construction of staggered contour trenches (2.5 m x 0.45 m x 0.45 m) spaced 2 m apart have completely controlled the runoff from a hilly area 4 to 5 ha.

Flood Control Reservoirs:

Small flood control reservoirs constructed in the head reaches have a solubrious effect on minimising damage down below. Water stored in such reservoirs can be recycled for irrigation. It can also be used for town water supply, power production, fish culture, etc.

The reservoir sides can be well developed for recreational purposes. Generally, two types of reservoirs are common in watersheds. One, flood storage reservoir and second detention reservoir.

The detention reservoirs operate automatically by discharging through one or more openings of constant dimensions in the dam (Fig. 11.5), whereas the storage reservoir discharges through adjustable gates. The chief advantage of the flood storage reservoir is its flexibility of operation.

The detention reser­voirs have emergency spillways to handle runoff in excess of the design flood. The principal advantages are its simplicity and automatic operation without personnel. Practically all headwater flood control reservoirs are of detention type.

Reservoirs for flood control reduce flood peaks, but not flood volumes. The reduction in peak flow diminishes rapidly with distance downstream since the main stream receives an increasing percentage of its runoff from other tributaries. The principal disadvantages of reservoir are that they occupy some land which remains flooded and that the annual and initial costs are high.

Underground Storage:

Underground storage is accomplished by spreading the flow over a consider­able area. In general, this is applicable only in arid regions. This is very effec­tive in raising the groundwater tables in the watershed. In areas where groundwater is considered as a potential source of irrigation water, this prac­tice is very useful.

Channel Improvement:

Channel improvement includes those measures that increase the channel capacity, such as enlarging the cross-sectional area of the channel and increas­ing the flow velocity. Cross-section of the channel can be increased either by deepening or widening the channel or by removing trees and sandbars from the water course to increase the channel effectiveness.

As evident from Manning’s equation, the velocity of flow can be increased by:

(1) Removing debris and vegetation to reduce surface roughness;

(2) Widening or deepening the channel to increase hydraulic radius; and

(3) By increasing the channel slope through deepening, straightening or lowering the water level at the outlet.

Deepening the channel or lowering the water level at the outlet can be accomplished by increasing the cross-sectional area at the outlet and removing debris or sandbars. For the same cross-sectional area, deepening is more effective than widening.

Channel Straightening:

The principal method of straightening streams is to provide cutoffs. A cutoff is a natural or artificial channel which shortens a meandering stream. The pur­pose of cutoff is to increase flow velocity, shorten the channel length and decrease the length of levees.

Sometimes the length of the stream is shortened as much as one-half the original length by channel straightening. It is desirable to provide cutoff where the stream capacity in the bend is less than the capacity in the other parts of the channel; the capacity of the entire channel is to be increased with levees; construction of the cutoff is more economical than in­creasing the capacity around the bend; and the cutoff does not detrimentally affect the flow characteristics of the stream.

Cutoffs increase the velocity in the affected portion of the stream by increas­ing the hydraulic gradient. In a meandering stream cutoffs may also occur naturally due to erosive forces of water. An example of the cutoff in a meandering stream is illustrated in Fig. 11.6. Before the cutoff, the stream flowed on a uniform slope around the bend BEG.

After the stream is straightened, it flows from B directly to E, which is about one-fourth of its pre­vious length (Fig. 11.6b). Because of the increased slope from B to E, the velocity is increased from to V₂ (Fig. 11.6c) with a corresponding decrease in the depth of flow. The decreased depth causes the water surface to be lowered to a point A upstream (Fig. 11.6c). In section CD, the velocity is V₂, which decreases afterwards but more than at A till it reaches to F.

Levees:

Levees are embankments along streams or on flood plains designed to confine the river flow to a definite width for the protection of surrounding land from overflow. Levees may be designed either to confine the river flow for a considerable distance or to provide local protection.

The effect of confining water between levees is to increase the water surface elevation during floods, to increase the maximum discharge downstream, to increase the rate of travel of the flood-wave, and to decrease the surface slope of the stream above. In narrow flood plains, channel improvement as well as channel straightening is usually more economical than levees.

B. Preventive Maintenance:

Preventive measures for maintaining the capacity of the stream channel in­clude, those which affect erosion in the channel itself, and those which reduce sediment from upper tributaries. Maintenance in the channel is required to prevent the collection of debris and to reduce sediment from caving banks.

The two classes of bank protection are:

(i) Those which retard the flow along banks and cause deposition, and

(ii) Those which cover the banks and prevent erosion.

A common method of control to retard the flow along banks and encourage soil deposition is to build retards extending into the stream from the banks. Materials to construct these retards include piles, trees, rocks, and steel fram­ing. Such retards serve to decrease the velocity along the can-cave bank and, hence, increase deposition of sediment.

Similarly, common methods for preventing stream bank erosion include both vegetative and mechanical. Grasses, shrubs and trees have been found effective vegetative control measures. Mechanical measures to cover the stream bank include such devices as wood and concrete mattresses, rock or stone, asphalt and sacked or monolithic concrete.

Reduction of Sediment and debris:

Sediment from high velocity streams in cultivated watersheds is deposited on flood plain areas and in the stream channels. Such sediments reduce the effec­tiveness of drainage ditches and the productivity of agricultural land.

Sediment and debris in stream channels can be reduced by deposition in suitable settling basins or by land treatments. Sedimentation and debris basins have three essential features, an inlet, a settling basin, and an outlet. Sediment-laden water from a stream may be diverted into a large set­tling basin where a portion of sediment is deposited as a result of reduced velocities.

At the lower end of the basin, the flow is then returned to the stream channel. Such settling basins are eventually filled with sediments, thus neces­sitating cleanout or the use of a new area.

It has also been found suitable to adopt barrier system of removing debris and sediment from mountain streams. Large debris is deposited as the flood spreads out at the mouth of the canyon and the finer material settles out in a settling basin.

Project Report # 7. Socio-Economic Aspects of Watershed Management:

A watershed is the natural unit for economic management and, therefore, in its management besides the Government view point, the view point of individuals and communities, who live in the watershed should also be considered. The people have their needs, custom values, and, therefore, the measures taken for the treatment of the watershed should have compatibility with the needs of the people.

Proper management of watershed, therefore, requires not only the knowledge and application of scientific techniques, but also substantial invest­ments of labour and capital whose returns may be high only in the long run and thus incompatible with the perspective of the farmer. How to motivate the farmers to make the necessary investment and sacrifice is a socio-economic problem.

The most important economic aspect of watershed management is to deter­mine whether the investment decisions on such programmes are rational. There are alternative techniques of soil conservation, water harvesting, storage and conveyance of water, alternative cropping patterns and technology pack­age for making optimum use of available water, etc.

It is the job of the economist to evaluate these alternatives and suggest the efficient one. Several techniques like benefit cost analysis, interval rate of return, etc. are available for evaluating such projects.

A study of the benefit cost analysis of a hill region watershed (Table 11.3) conducted by Central Soil and Water Conservation Research and Training In­stitute, Dehradun, indicated that even if benefit cost ratio of soil and water conservation work was more than one the rate of adoption was very slow.

Several reasons are given for it as the farmers cycle is different from that of the conservationists. While the farmer works on a year to year basis, the conser­vationists cycle is 25 years or so. From the farmers view point, it is very impor­tant to find out the factors that determine the rate of adoption of improved methods of soil conservation.

A study was conducted in the Ramganga watershed by G.B. Pant University of Agriculture and Technology, Pantnagar, to find out some of these factors.

On the basis of elevation, the Ramganga watershed is divided into three sub-watersheds, viz. upper Ramganga, middle Ramganga and lower Ramganga. A list of all the Gram Sabhas in each sub-watershed was prepared and two Gram Sabhas from each sub-watershed were selected at random.

A complete list of all the farmers, in the six selected Gram Sabhas, was prepared and the farmers in each Gram Sabha were divided into two groups, viz. adopters and non-adopters.

An adopter was defined as a farmer, who had adopted all the recommended methods of terracing, and a non-adopter was the one, who had not. A sample of 10% farmers from each group was drawn randomly from the six selected Gram Sabhas which constitute a sample of 90 farmers, 60 belonging to the adopter group and 30 to the non-adopter group.

The primary data was collected on a predesigned questionnaire and the secondary data were collected from the Forest Soil Conservation Division, Ranikhet and Ramnagar, in the agricultural year 1976-77. Analysis indicated that age of the head of the family and education level did not have any significant bearing on the per cent of total area under improved terracing.

The coefficients of the variables indicating number of parcels of land and the amount of subsidy were both statistically significant at 1% level of probability and had a negative and a positive sign, respectively. Therefore, number of parcels should be as few as possible.

Regarding subsidy, it is 50% at present. Results indicate that increase in subsidy shall further increase the area under improved terraces. The coefficients of the variable, indicating farm size, was significant at 2.5% level of probability and had a negative sign. This shows that the higher the farm size, the less would be the proportion of the area under terracing.

The data presented in Table 11.4 show an important role of livestock in the farm economy on hills. The livestock income is more than the crop income and the off farm income is as much as the livestock income though these decrease with the increase in the farm size.

In the hills, people keep large number of animals and migrate to the plains to supplement their farm income. Most of the agricultural operations are car­ried on by women. Alternative job opportunities in small and cottage in­dustries in the region itself and near their farms may help the situation.

In the Himalayan region, the land has been overgrazed, forests have been lopped and the hill sides have been denuded due to increase in both human and bovine population. The increase in demand has been much more than the regenerative capacity of the forests at the present level of technology and management.

One of the strategies of watershed management in the hills, therefore, is the encouragement of social forestry, forage husbandry and reduc­tion in the number of animals. A large number of milch animals are kept be­cause their productivity is low. A high yielding jersey breed could replace the local cows. Similarly, goats are also kept because it provides meat in the hills; and are thus very remunerative.

It is necessary to provide feed for them and find ways and means so that it does not cause any damage to the forests. Catties do provide manure to the farm land. Unless and until people need for fuel, fod­der, and timber is not met from alternative sources, damage to forests is bound to occur.

Therefore, to study the economic feasibility of watershed manage­ment and safeguard the individual benefits of the beneficiaries as well as the social benefits, the following have to be taken into consideration:

(a) Social objectives and interests of general public as custodian of natural resources,

(b) Development of backward areas,

(c) Growth of ancillary industries,

(d) Channelization of income of agricultural sector to productive use,

(e) Production of wages consumer goods,

(f) Encouragement of co-operative objectives, and

(g) Generalisation of employment.

Project Report # 8. Recent Trends in Watershed Management Research:

Watershed Models:

Because of complex interdisciplinary nature of predicting watershed perfor­mance, complex mathematical models have been postulated by several workers, in agricultural hydrology. These models are abstract, computerised devices for simulating the hydrologic processes that occur during the conver­sion of precipitation to stream flow.

Their use in conjunction with available information on soils, land use, geology and stream channel characters enables one to predict the spatial and temporal sequences in hydrology of watersheds. The more comprehensive models incorporate the ability to assess the influence of land use changes and structural works on stream flow from a watershed when it is subjected to a rainstorm or series of precipitation events.

Quick Evaluation of Watershed Potentials:

Preparation of watershed inventory provides a good opportunity for a big step forward within a short time. Probability sampling techniques adopting random sampling design may be used for preparation of soil and land resource inven­tory data for watershed development planning.