Introduction
Our environment is progressively degraded due to over exploitation of natural resources.
Population pressure indiscriminate tree felling, over grazing, unsound agricultural practices, all these and other factors contribute towards this degradation.
In the degraded landscape with little or no tree cover and subsequently little soil cover, the rain water is not able to percolate into the ground and flows away to the streams.
Along with this water we lose rich top soil which is necessary for any vegetation to grow.
It is a vicious cycle no top soil means no vegetation which leads to increase run off water and further erosion of top soil.
Why Watershed?
Waters are flowing to streams and joining to sea or oceans means there is little or no contribution for rain water to be absorbed by soil which means that the ground water level is decreasing so rather that exploitation of water we have to arrange for refilling of the water and also prevent the fertile soil to get eroded.
Objective
Primary objective of the programme is to conserve our natural resources the top six inches of the land are most fertile and most of the soil nutrients are present in that layer, the top soil is eroded with flowing water every year we have to prevent that.
Similarly the rain water also flows away and needs to be stopped; the speed of the flowing water has to reduce so that it doesn’t wash away the top soil so the basic work involves soil and water conservation.
It’s like a bank if you have money in the bank only then we can withdraw similarly the bank of our watershed is our hills if there are enough trees grasses and different kinds of treatment then the hills can conserve or store water inside them.If there is enough shade then the rain water will not directly impact onto the soil but rather its impact will be cushioned by the leaves of the trees or vegetative cover otherwise the water would be carried away by the loose top soil with its force.So we don’t just have to stop the water but also have to cover it i.e., to protect it direct rainfall sunlight and animals.
What is Watershed?
Along Centuries human beings have settled across rivers of catchment area which form lakes and provide regular supply of water to them
Watershed of a particular river or stream is defined as that area which collects the rain water and drains it into gully’s and nala bunds to a point on that river or stream. It may be small consisting of few hectares and huge covering several millions of hectares.
Delineation of a Watershed
Delineation of a watershed mean determining the boundary of the watershed i.e. ridgeline.
A watershed consists of three types of linesRidge Line, Drainage Line and Contour Lines.
After knowing the concept of watershed, it becomes important to see how a watershed can be identified on the site.
The watershed of any size can be delineated from the following:
1. Ridge Line
2. Outlet (Drainage Line)
Ridge Line is the line that joins comparatively the highest elevation points and that becomes the boundary of the watershed. A ridgeline bifurcates the falling water on two opposite sides.
The most important aspect for defining and delineating a watershed is to fix the outlet of the drainage course. As the outlet goes downstream of the drainage course, the area of the watershed goes on increasing. Basically location (position) of the outlet defines the area of watershed.
Watersheds are classified based on the area (size):
• Micro watershed (upto 10 ha)
• Mini watershed (upto 200 ha)
• Sub watershed (upto 4000 ha)
• Watershed (upto 10,000 ha)
• River basin or River valley ( more than 10,000 ha)
Watersheds are of different types based on their location:
• Runoff watershed or ”A” class watershed (Upper reach watershed): These watersheds are at the origin of river or at the upper catchment of river basin. Runoff is the main characteristic here.
• Recharging watershed or ”B” class watershed (Middle reach watershed): These are on the plateau area characterised by medium percolation and infiltration.
• Storage watershed or ”C” class watershed (Lower reach watershed): These watersheds are in the plains and characterised by good infiltration and recharging.
Watersheds are also based on the ground water exploitation:
• Dark watershed: In these watersheds annual ground water pumping is more than 85 % of annual recharging. These watersheds are also called fully “developed” (exploited) watersheds.
• Grey watershed: In these watersheds annual ground water drafting is 65 – 85 % of annual recharging.
• Yellow watershed: In theses watersheds annual ground water drafting less than 65% of annual recharging. These are called as least developed or exploited watershed.
The dark watersheds need to be treated on the priority basis.
Watersheds can be of different shapes:
• Square
• Rectangular
• Triangular
• Polygonal
The volume of water at the outlet of the watershed depends on the shape of the watershed and hence this needs to be taken into consideration while planning treatments for the watershed.
While planning for development of any watershed, one needs to look deeply into various aspects:
• The size, shape, average slope of the watershed
• Vegetation and land use
• Soil texture, depth of soil, geology
• Average annual rainfall, rainfall period and its distribution, rainfall intensity and frequency, infiltration rate
What will Watershed Management do?
Watershed management is treatment of the entire catchment area and an attempt to regeneration conservation and judicious use of all resources natural like plants water land animals within a particular watershed can be referred to as watershed management.
Watershed development must be run from ridge to valley basis.
The main objective behind watershed developments treatments is to reduce the velocity of fast flowing water and increase the time of concentration which will allow the water to percolate and recharge the subsurface aquifers.
Watershed development programme has to be undertaken from the top most point where the rain water after flowing starts flowing downwards this point is called the Ridge.
The watershed has to start from the ridge and progress downwards to the valley. There are reasons for this firstly soil conservation is essential for watershed development if only water storage structures are built the purpose of halting soil erosion is defeated. The soil gets washed away and collects in these structures due to this silt gets deposited over the years and the structure gets filled with the soil this leads to reduction in its capacity to store water thus neither soil and nor the water is conserved.
Secondly if there are no barriers at the ridge the water will flow down at such a high rate/velocity that it’ll wash away the water storage structure below or the structures has to be strong enough to withstand the velocity this means an additional expenditure.
Watershed developments are to be down along the contour lines these are the lines joining the points that are at the same altitude or height. This ensures the water that collects at the treated area remains at the uniform level leading to even moisture throughout the land.
It also reduces the chances of the structure breaking as the water pressure at all point on the treatment is the same.
From top of the hills downwards the series of structures is made that would ensure step by step slowing down the fast flowing of water until a part of it finally stopped. This results in control of erosion retention of soil fertility better soil moisture infiltration and ground water recharge
Area treatment in Non-Arable Waste Land
• Water absorption trenches
• Continuous contour trenches
• Stone bunds
Water Absorption Trenches (WAT)is large size trench excavated along the contour line with the cross section of 1sq meter. It is usually excavated on highly degraded waste land where the slope is steep and sudden changes in the slope. To trap rain water enable it to percolate to underground aquifers and break the speed of fast moving water Continuous Contour Trenches(CCT)are excavated. Besides helping in percolation these CCT increase soil moisture which help in the growth of grass shrubs and trees.
Depending upon the rainfall the dimensions of the CCT will vary and so will the required volume of earth work per hectare. Since fodder is basic requirement in rural livelihood grasses of nutritional variety can be planted across the mounds of that and CCT as well as beds between the CCT. This not only provides fodder for animals it also prevents the soil erosion. When degraded land require plantation the CCTs are refilled. The top soils from the upstream side are filled in the CCT.
After digging the CCT will refill them. On the hill we have the CCT which is 30cm wide, we dig soil from the upstream side up to 1m above the CCT and put this soil into the CCT.The height of the soil column that is refilled in the CCT should be around 45 – 60cm from the bottom of the CCT and in the centre of the refilled portion we plant trees.
This treatment results in good survival rate of plants generally in place where soil depth is little. It allows proper aeration and prevents root coiling and creates a moisture bank so necessary for plant growth especially in arid areas.
On the CCTs which are suitably weathered and refilled with earth, trees grasses and shrubs are planted.
These are usually local species which meets the local needs of fuel fodder timber fruits and fiber. Where the soil depths are not sufficient the pastures are developed.
Where there is enough soil depth CCT’s are doneup to 30 cm deep these are dug across the slope and maintaining the same level. Where ever the terrain is rocky and there is not enough soil we make Bunds using stones.
Stone bunds are laid along the contour lines across the slope to arrest the flow of water and control erosion in areas where soil excavation work is not possible. Stone bunds can be erected in both arable and not arable lands.
Area Treatment on Cultivable Land.
• Farm bunds.
• Contour bunds.
• Waterways and outlets.
Watershed development also involves taking up of area treatments in cultivable lands. Here the objective is to increase the productivity of the land for crops & horticulture through different soil and water conservation measures.
Farm bund is useful areas where the land is almost flat or used for agricultural purposes.
Farm bunds are erected across the slopes if not possible across the boundaries of the fields.
The top level of the bund should be even throughout so that required cross section is maintained irrespective of undulations of the plot. Grasses and trees can be grown for better stability and additional income for the farmer.
Earthen bund raised along the counter line is called Contour Bund. Waterways outlets either natural or artificially constructed are necessary for safe disposal of additional water from the field in a manner that minimizes erosion. Outlets are built to remove excess runoffs from the farm or Counter Bund.
Normally outlets are built at a height up to 1 foot from the ground level so as to stew some runoff.
Two types of outlets are used the Stone Outlets and the Pipe Outlets.
Drainage line treatemets
• Gully Plugs
• Nala Bunds
• Gabion Structures
• Loose Boulder Structures
• Masonry Structures
A series of structures is constructed along the drainage line these structures allow the surplus run off which has been considerably slowed down to accumulate and get stored along the entire drainage line.Which ensures entire groundwater recharge and creation of water banks.
Gully plugs are usually makeup of loose rocks of stones which are locally available.
Vegetation is necessary for the stabilization of the gully.
Earthen Gully Plugsare the earthen embankments which are built across the slopes situated at the bed of the gully. A spillway is provided at any one side of the embankment to bring the excess runoff at the non-erosive velocity
When gullies are prominent instead of small side gully plugs loose boulder structures with batter sometimes on both sides are constructed
Gabion Structures is similar to loose boulder structure but to increase stability the boulders are enmeshed in wire. Gabion structure is constructed in places where the foundation is not available for the construction of check dam or there is no possibility of a spillway to construct a nala bund.
Gabion Structures are silt controlled measures but through some innovation such as central concrete wall or plastering it can be converted into a water harvesting structure
NalaBundis an earthen bund of suitable dimension raised across nala or gully the purpose is to hold the run off in order to create a pond or water body on the upstream side of the bund
Nala bund is always constructed with the facility of spill way for draining surplus of rain water. These structures store rain water for a particular amount of time which helps recharging of ground water. Nala bunds also help to stabilize nalas,gully’s and streams
Check Damsare masonry structures which are constructed to impound surplus runoff, the stored water recharges the underground water this type of structures is constructed when in nala bund or in earthen structures cannot be need or a site where a spill way is not available
The objective of the different treatment is to meet the barren lands productive for forests pastures and agriculture.
If we start the work from the bottom and move up what are the disadvantages.
If we start the work from the bottom then as there is no such things as bunds and counter lines in the top there will be no resistance for the water flow and as it come with such velocity from the top that by the time the work at lower is completed it’ll will be destroyed.
Mythology
Once King Bhagirathi wanted to bring River Ganga from heaven but Ganga would fall from such a force that the earth would not be able to withstand the pressure so the Lord Shiva slowed the impact of the fall by taking it on this head on which his hair was tied. The water has to go through his hair and fall’s pressure was controlled.
i.e., pressure of rain water falling on the earth is to be reduced so that water would flow without eroding the soil
By doing watershed work form ridge to valley we do it the way the nature is intended. Running water is slowed down flowing water is made to walk and walking water is stopped. Spread around and made to go underground this is what that the rain water a nurturing nourishing cause of life peace and prosperity.
Summary
Treatment of the entire catchment area around the entire village to ensure conservation and regeneration of all its natural resources especially Water is called Watershed Development.
Watershed development must be run from ridge to valley basis.
Right from the top you dig continuous contour trenches and when you come down on waste lands you dig continuous contour bunds and on farm land you erect farm bunds along the drainage line of the rivers right from the top you do gully plugs when you come down nalabunds, gabion structures and check dams.
The idea is to control soil erosion and to control the flow of gushing water; water that is running we try to make it walk, walking water we stop and stop water we try to force it under ground. The idea is to trap harvest and store the rain water where ever it falls within the area itself. Since the speed of the rain water is controlled and the soil is not washed away the rivers doesn’t get flooded and silted.
Thus the water shed development is an answer to two problems that of drought and that of that of fly.
Earlier method of watershed development concentrated merely on the harvesting structures and ignored treating water shed as a home therefore this lead to soil erosion and siltation.
by Prasad MV
Our environment is progressively degraded due to over exploitation of natural resources.
Population pressure indiscriminate tree felling, over grazing, unsound agricultural practices, all these and other factors contribute towards this degradation.
In the degraded landscape with little or no tree cover and subsequently little soil cover, the rain water is not able to percolate into the ground and flows away to the streams.
Along with this water we lose rich top soil which is necessary for any vegetation to grow.
It is a vicious cycle no top soil means no vegetation which leads to increase run off water and further erosion of top soil.
Why Watershed?
Waters are flowing to streams and joining to sea or oceans means there is little or no contribution for rain water to be absorbed by soil which means that the ground water level is decreasing so rather that exploitation of water we have to arrange for refilling of the water and also prevent the fertile soil to get eroded.
Objective
Primary objective of the programme is to conserve our natural resources the top six inches of the land are most fertile and most of the soil nutrients are present in that layer, the top soil is eroded with flowing water every year we have to prevent that.
Similarly the rain water also flows away and needs to be stopped; the speed of the flowing water has to reduce so that it doesn’t wash away the top soil so the basic work involves soil and water conservation.
It’s like a bank if you have money in the bank only then we can withdraw similarly the bank of our watershed is our hills if there are enough trees grasses and different kinds of treatment then the hills can conserve or store water inside them.If there is enough shade then the rain water will not directly impact onto the soil but rather its impact will be cushioned by the leaves of the trees or vegetative cover otherwise the water would be carried away by the loose top soil with its force.So we don’t just have to stop the water but also have to cover it i.e., to protect it direct rainfall sunlight and animals.
What is Watershed?
Along Centuries human beings have settled across rivers of catchment area which form lakes and provide regular supply of water to them
Watershed of a particular river or stream is defined as that area which collects the rain water and drains it into gully’s and nala bunds to a point on that river or stream. It may be small consisting of few hectares and huge covering several millions of hectares.
Delineation of a Watershed
Delineation of a watershed mean determining the boundary of the watershed i.e. ridgeline.
A watershed consists of three types of linesRidge Line, Drainage Line and Contour Lines.
After knowing the concept of watershed, it becomes important to see how a watershed can be identified on the site.
The watershed of any size can be delineated from the following:
1. Ridge Line
2. Outlet (Drainage Line)
Ridge Line is the line that joins comparatively the highest elevation points and that becomes the boundary of the watershed. A ridgeline bifurcates the falling water on two opposite sides.
The most important aspect for defining and delineating a watershed is to fix the outlet of the drainage course. As the outlet goes downstream of the drainage course, the area of the watershed goes on increasing. Basically location (position) of the outlet defines the area of watershed.
Watersheds are classified based on the area (size):
• Micro watershed (upto 10 ha)
• Mini watershed (upto 200 ha)
• Sub watershed (upto 4000 ha)
• Watershed (upto 10,000 ha)
• River basin or River valley ( more than 10,000 ha)
Watersheds are of different types based on their location:
• Runoff watershed or ”A” class watershed (Upper reach watershed): These watersheds are at the origin of river or at the upper catchment of river basin. Runoff is the main characteristic here.
• Recharging watershed or ”B” class watershed (Middle reach watershed): These are on the plateau area characterised by medium percolation and infiltration.
• Storage watershed or ”C” class watershed (Lower reach watershed): These watersheds are in the plains and characterised by good infiltration and recharging.
Watersheds are also based on the ground water exploitation:
• Dark watershed: In these watersheds annual ground water pumping is more than 85 % of annual recharging. These watersheds are also called fully “developed” (exploited) watersheds.
• Grey watershed: In these watersheds annual ground water drafting is 65 – 85 % of annual recharging.
• Yellow watershed: In theses watersheds annual ground water drafting less than 65% of annual recharging. These are called as least developed or exploited watershed.
The dark watersheds need to be treated on the priority basis.
Watersheds can be of different shapes:
• Square
• Rectangular
• Triangular
• Polygonal
The volume of water at the outlet of the watershed depends on the shape of the watershed and hence this needs to be taken into consideration while planning treatments for the watershed.
While planning for development of any watershed, one needs to look deeply into various aspects:
• The size, shape, average slope of the watershed
• Vegetation and land use
• Soil texture, depth of soil, geology
• Average annual rainfall, rainfall period and its distribution, rainfall intensity and frequency, infiltration rate
What will Watershed Management do?
Watershed management is treatment of the entire catchment area and an attempt to regeneration conservation and judicious use of all resources natural like plants water land animals within a particular watershed can be referred to as watershed management.
Watershed development must be run from ridge to valley basis.
The main objective behind watershed developments treatments is to reduce the velocity of fast flowing water and increase the time of concentration which will allow the water to percolate and recharge the subsurface aquifers.
Watershed development programme has to be undertaken from the top most point where the rain water after flowing starts flowing downwards this point is called the Ridge.
The watershed has to start from the ridge and progress downwards to the valley. There are reasons for this firstly soil conservation is essential for watershed development if only water storage structures are built the purpose of halting soil erosion is defeated. The soil gets washed away and collects in these structures due to this silt gets deposited over the years and the structure gets filled with the soil this leads to reduction in its capacity to store water thus neither soil and nor the water is conserved.
Secondly if there are no barriers at the ridge the water will flow down at such a high rate/velocity that it’ll wash away the water storage structure below or the structures has to be strong enough to withstand the velocity this means an additional expenditure.
Watershed developments are to be down along the contour lines these are the lines joining the points that are at the same altitude or height. This ensures the water that collects at the treated area remains at the uniform level leading to even moisture throughout the land.
It also reduces the chances of the structure breaking as the water pressure at all point on the treatment is the same.
From top of the hills downwards the series of structures is made that would ensure step by step slowing down the fast flowing of water until a part of it finally stopped. This results in control of erosion retention of soil fertility better soil moisture infiltration and ground water recharge
Area treatment in Non-Arable Waste Land
• Water absorption trenches
• Continuous contour trenches
• Stone bunds
Water Absorption Trenches (WAT)is large size trench excavated along the contour line with the cross section of 1sq meter. It is usually excavated on highly degraded waste land where the slope is steep and sudden changes in the slope. To trap rain water enable it to percolate to underground aquifers and break the speed of fast moving water Continuous Contour Trenches(CCT)are excavated. Besides helping in percolation these CCT increase soil moisture which help in the growth of grass shrubs and trees.
Depending upon the rainfall the dimensions of the CCT will vary and so will the required volume of earth work per hectare. Since fodder is basic requirement in rural livelihood grasses of nutritional variety can be planted across the mounds of that and CCT as well as beds between the CCT. This not only provides fodder for animals it also prevents the soil erosion. When degraded land require plantation the CCTs are refilled. The top soils from the upstream side are filled in the CCT.
After digging the CCT will refill them. On the hill we have the CCT which is 30cm wide, we dig soil from the upstream side up to 1m above the CCT and put this soil into the CCT.The height of the soil column that is refilled in the CCT should be around 45 – 60cm from the bottom of the CCT and in the centre of the refilled portion we plant trees.
This treatment results in good survival rate of plants generally in place where soil depth is little. It allows proper aeration and prevents root coiling and creates a moisture bank so necessary for plant growth especially in arid areas.
On the CCTs which are suitably weathered and refilled with earth, trees grasses and shrubs are planted.
These are usually local species which meets the local needs of fuel fodder timber fruits and fiber. Where the soil depths are not sufficient the pastures are developed.
Where there is enough soil depth CCT’s are doneup to 30 cm deep these are dug across the slope and maintaining the same level. Where ever the terrain is rocky and there is not enough soil we make Bunds using stones.
Stone bunds are laid along the contour lines across the slope to arrest the flow of water and control erosion in areas where soil excavation work is not possible. Stone bunds can be erected in both arable and not arable lands.
Area Treatment on Cultivable Land.
• Farm bunds.
• Contour bunds.
• Waterways and outlets.
Watershed development also involves taking up of area treatments in cultivable lands. Here the objective is to increase the productivity of the land for crops & horticulture through different soil and water conservation measures.
Farm bund is useful areas where the land is almost flat or used for agricultural purposes.
Farm bunds are erected across the slopes if not possible across the boundaries of the fields.
The top level of the bund should be even throughout so that required cross section is maintained irrespective of undulations of the plot. Grasses and trees can be grown for better stability and additional income for the farmer.
Earthen bund raised along the counter line is called Contour Bund. Waterways outlets either natural or artificially constructed are necessary for safe disposal of additional water from the field in a manner that minimizes erosion. Outlets are built to remove excess runoffs from the farm or Counter Bund.
Normally outlets are built at a height up to 1 foot from the ground level so as to stew some runoff.
Two types of outlets are used the Stone Outlets and the Pipe Outlets.
Drainage line treatemets
• Gully Plugs
• Nala Bunds
• Gabion Structures
• Loose Boulder Structures
• Masonry Structures
A series of structures is constructed along the drainage line these structures allow the surplus run off which has been considerably slowed down to accumulate and get stored along the entire drainage line.Which ensures entire groundwater recharge and creation of water banks.
Gully plugs are usually makeup of loose rocks of stones which are locally available.
Vegetation is necessary for the stabilization of the gully.
Earthen Gully Plugsare the earthen embankments which are built across the slopes situated at the bed of the gully. A spillway is provided at any one side of the embankment to bring the excess runoff at the non-erosive velocity
When gullies are prominent instead of small side gully plugs loose boulder structures with batter sometimes on both sides are constructed
Gabion Structures is similar to loose boulder structure but to increase stability the boulders are enmeshed in wire. Gabion structure is constructed in places where the foundation is not available for the construction of check dam or there is no possibility of a spillway to construct a nala bund.
Gabion Structures are silt controlled measures but through some innovation such as central concrete wall or plastering it can be converted into a water harvesting structure
NalaBundis an earthen bund of suitable dimension raised across nala or gully the purpose is to hold the run off in order to create a pond or water body on the upstream side of the bund
Nala bund is always constructed with the facility of spill way for draining surplus of rain water. These structures store rain water for a particular amount of time which helps recharging of ground water. Nala bunds also help to stabilize nalas,gully’s and streams
Check Damsare masonry structures which are constructed to impound surplus runoff, the stored water recharges the underground water this type of structures is constructed when in nala bund or in earthen structures cannot be need or a site where a spill way is not available
The objective of the different treatment is to meet the barren lands productive for forests pastures and agriculture.
If we start the work from the bottom and move up what are the disadvantages.
If we start the work from the bottom then as there is no such things as bunds and counter lines in the top there will be no resistance for the water flow and as it come with such velocity from the top that by the time the work at lower is completed it’ll will be destroyed.
Mythology
Once King Bhagirathi wanted to bring River Ganga from heaven but Ganga would fall from such a force that the earth would not be able to withstand the pressure so the Lord Shiva slowed the impact of the fall by taking it on this head on which his hair was tied. The water has to go through his hair and fall’s pressure was controlled.
i.e., pressure of rain water falling on the earth is to be reduced so that water would flow without eroding the soil
By doing watershed work form ridge to valley we do it the way the nature is intended. Running water is slowed down flowing water is made to walk and walking water is stopped. Spread around and made to go underground this is what that the rain water a nurturing nourishing cause of life peace and prosperity.
Summary
Treatment of the entire catchment area around the entire village to ensure conservation and regeneration of all its natural resources especially Water is called Watershed Development.
Watershed development must be run from ridge to valley basis.
Right from the top you dig continuous contour trenches and when you come down on waste lands you dig continuous contour bunds and on farm land you erect farm bunds along the drainage line of the rivers right from the top you do gully plugs when you come down nalabunds, gabion structures and check dams.
The idea is to control soil erosion and to control the flow of gushing water; water that is running we try to make it walk, walking water we stop and stop water we try to force it under ground. The idea is to trap harvest and store the rain water where ever it falls within the area itself. Since the speed of the rain water is controlled and the soil is not washed away the rivers doesn’t get flooded and silted.
Thus the water shed development is an answer to two problems that of drought and that of that of fly.
Earlier method of watershed development concentrated merely on the harvesting structures and ignored treating water shed as a home therefore this lead to soil erosion and siltation.
by Prasad MV
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