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 OFWATERSHED 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 OF WATERSHEDDEVELOPMENT 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 ANDPOLITICAL 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 FORWATERSHED MANAGEMENTAND 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 SETUP District Watershed Development Advisory Committee Project Implementation Agency Watershed Development Team Watershed Development Community Village Development committee
STEPS FOR PREPARATION OFINTEGRATED WATERSHEDMANAGEMENT PLANPreparation of watershed development plan includes twomain 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.
SOIL SOIL PROPERTIES: PHYSICAL SAND SILT CLAY POROSITY MOSTLY SMALL SMALL LAGRE PORES PORES PORES PREDOMINAT PREDOMINAT E E PERMEABILI RAPID LOW TO SLOW TY MODERATE WATER LIMITED MEDIUM VERY LARGE HOLDING CAPACITY SOIL SMALL MEDIUM VERY LAGE PARTICLE SURFACE
SOILPROPERTIES:CHEMICAL VARIES FROOM 0 TO 14 pH (ALKALINE /ACIDIC /NUETRAL SOILS) EASILY LEACHED OUT CHEMICALS (Chlorides and Sulphates, AND ELEMENTS followed by Calcium, Sodium, Magnesium and PRESENT 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 WATERCONSERVATION MEASURES FORWATERSHED 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 CONSERVATIONMEASURES 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 BUNDINGThese are constructed where the excess water is to beremoved safely to avoid water stagnation. In thesewater flows in graded channel constructed on theupstream side of the bunds at non erosive velocitiesand 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 FORNON-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
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.
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 REDUCTION OF PORE WATER PRESSURE INCREASE SHEAR STRENGTH OF SLIDING SURFACE CONTROL WORK PREVENTIONMECHANICAL OF SOILCOUNTER- EROSIONMEASURES REFORM SLOPE PILE PREVENTIVE WORK ANCHOR
WATERSHED AND DRAINAGEPATTERNS 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 OFWATERSHED 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.