WATERSHED MANAGEMENT AND DEVELOPMENT

CONTENTS Watershed and its importance. Watershed management and its objectives

and perspectives. Approach for watershed management. Geological aspects- natural resources and

hazards. Watershed and drainage patterns. Individual contributions towards watershed.

WATERSHED A WATERSHED can be defined as a geo-

hydrological unit that drains to a common point by a system of drains. All lands on earth are a part of one watershed or another.

The words watershed ,catchment ,basin, drainage area, are synonymous , and in Indian usage, pertain to an area and not a line.

The terms micro, mini, sub-watershed or any other variation of the terms indicate hierarchical division of the watershed of a stream, river or a drainage line.

IMPORTANCE OF WATERSHEDS Watersheds sustain life, in more ways than

one.  According to the Environmental Protection

Agency, more than $450 billion in foods, fibre, manufactured goods and tourism depend on clean, healthy watersheds.

Healthy watersheds are also important for the very sustenance of human life

WATERSHED MANAGEMENT Watershed management is defined as the

process of formulating and carrying out course of action involving manipulation of natural, agricultural and human resources of a watershed to provide resources that are desired by and are suitable to the watershed community

The watershed management and exploitation should not have any adverse effects on soil and water resources

It is an integrated and multidisciplinary approach.

OBJECTIVES OF WATERSHED MANAGEMENT Protecting, conserving and improving the

land resources for efficient and sustained production.

Protecting and enhancing water resources, moderating floods, reducing silting up of tanks/reserviors, increasing irrigation and conserving rainwater for crops and thus mitigating droughts

Utilizing the natural local resources for improving agriculture and allied occupation of industries so as to improve socio-economic conditions of local residents.

PERSPECTIVES ON WATERSHED MANAGEMENT

PERSPECTIVES OF WATERSHED DEVELOPMENT HYDROLOGICAL ASPECTS ENVIRONMENTAL ASPECTS SOCIO-ECONOMIC ASPECTS FINANCIAL ASPECTS ADMINISTRATIVE AND POLITICAL ASPECTS

HYDROLOGICAL ASPECTS Hydrological behaviour of watershed is

influenced by watershed conditions. The watershed treatment and management

practices alter the slope and roughness characteristics of the watershed management and tend to reduce the surface flow and the peak flow

The management practices also reduce the rate and quantity of the sediment erosion and their transportation resulting in lower delivery of sediments into the reservoir

These measure effects flood control, soil moisture conservation and land use.

ENVIRONMENTAL ASPECTS Development applied locally for developing

green foliage, enriches environment globally in due course of time.

The local measure of micro-scale watershed development would have cumulative effect on environment when considered on a large basin or a global scale

Reduced onsite erosion and enhance in a well managed watershed also improve the natural ecosystem

SOCIO-ECONOMIC ASPECTS In achieving the true objective of watershed

management, the viewpoint of individuals and communities, who live in the watershed should be considered.

The socio-economic factors also determine the motivation of farmers to make necessary investment of labour and capital in watershed development.

FINANCIAL ASPECTS The projects can either be fully funded by

government or NGOs or in case of the development the participating families may be required to contribute a predefined percentage of cost for individual works and for community work.

The unit cost for watershed development normally range from Rs. 4500 to Rs. 6000 per hectare depending on nature and location of the watershed.

ADMINISTRATIVE AND POLITICAL ASPECTS Watershed management requires close

collaboration of various planning and implementing agencies to achieve full benefits of the programme.

Planning should only include those measures/activities which are acceptable politically.

APPROACH FOR WATERSHED MANAGEMENT AND DEVELOPMENT People’s participation is the key to watershed

development programmes. While the main development activities have to be

carried out by the watershed community itself, the overall facilitation, coordination and supervision of the whole programme will be responsibility of a PROJECT IMPLEMENTATION AGENCY (PIA).

The whole setup for the watershed management follows a hierarchical approach.

ORGANISATIONAL SETUPDistrict Watershed Development

Advisory Committee Project Implementation

AgencyWatershed Development

TeamWatershed

Development Community

Village Development

committee

STEPS FOR PREPARATION OF INTEGRATED WATERSHED MANAGEMENT PLANPreparation of watershed development plan includes two main steps:1. Identification of watershed problems and setting

up of objectives and priorities based on various surveys of watershed.

2. Formulation of proposed development and management plan.

GEOLOGICAL ASPECTS OF WATERSHED MANAGEMENT AND DEVELOPMENT

GEOLOGI-CAL

ASPECTS

NATURAL RESOURCE

S

SOIL

WATER

NATURAL HAZARDS

EARTHQUAKES

FLOODS

LANDSLIDES

SOIL SOIL PROPERTIES: PHYSICAL

SAND SILT CLAY

POROSITY MOSTLY LAGRE PORES

SMALL PORES PREDOMINATE

SMALL PORES PREDOMINATE

PERMEABILITY

RAPID LOW TO MODERATE

SLOW

WATER HOLDING CAPACITY

LIMITED MEDIUM VERY LARGE

SOIL PARTICLE SURFACE

SMALL MEDIUM VERY LAGE

SOILPROPERTIES:CHEMICAL

pH VARIES FROOM 0 TO 14 (ALKALINE /ACIDIC /NUETRAL SOILS)

CHEMICALS AND ELEMENTS PRESENT

EASILY LEACHED OUT (Chlorides and Sulphates, followed by Calcium, Sodium, Magnesium and Potassium)

RARELY LEACHED (Silicates and Oxides of Iron and Aluminium)

WATER In case of water we consider water quantity

and water quality, where water quantity is imp to prevent floods and water logging, the concept water quality is important to delineate the uses for which water can be used from a given watershed.

WATER PROPERTIES:PHYSICAL

Formula: H2O Density: 1,000.00 kg/m³ Molar mass: 18.0153 g/mol Boiling point: 99.98° C Melting point: 0.0° C

WATER PROPERTIES: CHEMICAL

Chemically pure water should have only hydrogen and oxygen.

The water we use for daily purposes has a variety of other elements like Iron, Magnesium etc. but these elements should be under permissible limits prescribed for any purpose like drinking, agriculture etc.

Water should be of neutral pH, but presence of certain salts may make it acidic or basic.

SOIL AND WATER CONSERVATION MEASURES FOR WATERSHED TREATMENT Soil and water conservation measures to be

employed depend on the purpose for which the land and water is to be used. There are two broad categories:

1. SOIL AND WATER CONSERVATION MEASURES FOR AGRICULTURAL LAND.

2. EROSION CONTROL MEASURES FOR NON-AGRICULTURAL LAND.

SOIL AND WATER CONSERVATION MEASURES FOR AGRICULTURAL LAND

Contour bunding. Graded bunding or channel terraces. Bench terracing. Grassed waterways. Strip cropping Mulching Sub soiling

CONTOUR BUNDING• Contour bunding consists of constructing narrow-based

trapezoidal earthen embankment at intervals along the contour to impound run off water behind them so that all the stored water is absorbed gradually into the soil profile for crop use.

• A series of such bunds divide the area into strips and act as barrier to the flow of water.

GRADED BUNDING These are constructed where the excess water is to be removed safely to avoid water stagnation. In these water flows in graded channel constructed on the upstream side of the bunds at non erosive velocities and is led to safe outlets.

BENCH-TERRACING• It is practiced on steep hill slopes ranging

from 16-33%.• Bench terracing which involves converting

the original ground into level step like fields constructed by half cutting and half filling, helps in considerably reducing the degree of slope

GRASSED WATERWAYS• These are associated with channel terraces for

safe disposal of concentrated run-off, thereby protecting the land against rills and gullies.

• A waterway is constructed according to a proper design and a vegetative cover is established to protect the channel against erosion because of concentrated flow.

STRIP CROPPING• Strip cropping consists of a series of alternate

strips of various types of crops laid out so that all tillage and crop management practices are performed across the slope or on the contours.

• Strips of erosion –permitting crops are always separated by strips of close growing or erosion resisting crops .

MULCHING• Mulching of open land surface in a cropped area is

achieved by spreading stubble trash or any vegetation.

• These are used to minimize splash, to prevent soil from blowing or being washed away, to reduce evaporation, to increase infiltration, to control weeds, to improve soil quality and eventually increase crop yield.

SUB-SOILING• This method consists of breaking with a

subsoiler the hard and impermeable subsoil to conserve more rain-water by improving physical conditions of the soil.

EROSION CONTROL MEASURES FOR NON-AGRICULTURAL LAND

Contoured and staggered trenches for hill slopes.

Gully control.

CONTOURED AND STAGGERED TRENCHES

• Suitable erosion control in hills

• Adopted for hill slopes >20%

GULLY CONTROL STRUCTURE

Gully erosion usually starts as small rills and then develops into deeper crevices or Ravines in extreme cases.

it can be controlled by check dams which may be permanent, semi-permanent or temporary

Temporary check dams are usually made up of brush wood, wire and poles or loose rocks

Semi-permanent check dams can be earthen dam, Gabion structure etc.

Permanent check dams are concrete and masonry structures

GABION STR WOVEN WIRE

SPILLWAY

NATURAL HAZARDS FLOODS. EARTHQUAKES. LANDSLIDES.

FLOODS The management of rainfall and resultant run-off

is very important to control floods and found to depend on watersheds.

Due to floods, the plains have become silted with mud and sand that affect the cultivable lands, watershed management thus helps to reduce the rate and quantity of the sediment to be deposited.

The excess runoff from streams during monsoon can be controlled using techniques like check dams, percolation dams etc.

This results in mitigation of floods, recharge of ground water which can be used during times of drought.

PERCOLATION POND

EARTHQUAKES While developing a watershed the zone of

hazard in which the area falls must be kept in mind.

If lineaments such a folds, faults, joints etc. are more at a place (where watershed is to be developed) then the area is more earthquake prone

The structures developed must be earthquake resistant if the area is in a hazardous zone.

EARTHQUAKE PREPARATION The objective of earthquake engineering is to

foresee the impact of earthquakes on buildings and other structures and to design such structures to minimize the risk of damage.

Existing structures can be modified by seismic retrofitting  to improve their resistance to earthquakes.

Emergency management strategies can be employed by a government or organization to mitigate risks and prepare for consequences

LANDSLIDES A landslide is a geological

phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows.

Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released

LANDSLIDE PREVENTION

MECHANICAL

COUNTER-

MEASURES

PREVENTIVE WORK

PILE

ANCHOR

CONTROL WORK

REDUCTIONOF POREWATERPRESSURE

INCREASESHEARSTRENGTH OF SLIDING SURFACE

PREVENTIONOF SOIL EROSION

REFORMSLOPE

WATERSHED AND DRAINAGE PATTERNS The drainage patterns have effect on

watershed development as they decide the type of sedimentation processes the quantity of sediments and water.

The drainage patterns also give idea of lithology and relief, eg. the development of dendritic to sub dendritic drainage in the watershed indicates the area of massive rock types, gently sloping to almost horizontal terrain and low relief

It has been suggested that the parallel drainage in Deccan Basalt terrain is initiated due to the step like nature of the Deccan traps which is joined by subsequent lateral ravines giving a sub-parallel pattern (Dhokarikar, 1991)

SINCE EVERYONE IS A PART OF WATERSHED Don’t pour toxic household chemicals down

the drain; take them to a hazardous waste centre

Recycle yard waste in a compost pile & practice mulching.

Adopt your watershed.

THANK YOU