drought management and water harvesting m5
DESCRIPTION
Definition of drought, Causes of drought, measures for water conservation and augmentation, drought contingency planning. Water harvesting: rainwater collection, small dams, runoff enhancement, runoff collection, ponds, tanks.TRANSCRIPT
Drought Management and Water Harvesting
Prepared by Bibhabasu Mohanty
Dept. of Civil EngineeringSALITER, Ahmedabad
MODULE- V
Contents
Definition of drought, Causes of drought, measures for water conservation and augmentation, drought contingency planning.
Water harvesting: rainwater collection, small dams, runoff enhancement, runoff collection, ponds, tanks.
Introduction Normal, recurrent feature of climateOccurs everywhere, vary from
region to region.Originates from deficiency of
precipitation.Impact on ecosystem and
agricultural of affected region.Drought leads to food insecurity,
famine, malnutrition, epidemics and displacement of populations.
Types of drought
Meteorological drought
Agricultural drought
Hydrological drought
Socioeconomic drought
Causes of droughtReduced rainfall results in drought.Occurs because water vapour not
brought by air currents to right areas at right times.
Unusual currents of cold and warm water in oceans creates high pressure. El Nino causes drought in Asia.
Mountain prevent wind from blowing moisture to needy region.
In India when water vapour moves from east to west, water vapour does not leave Indian ocean causes drought.
Human activity directly trigger over farming, excessive irrigation, deforestation.
Global warming result in rainfall in some areas and drought in some areas.
Drought contingency planning
To provide contingency plans to manage drought and emergency conditions.
To continue to deliver a cost effective, adequate, safe and reliable supply of water.
The provision of credit or cash/food for work
Maintaining water supply for animals and humans
Maintaining cereal availabilityHuman and livestock health service
provisionSupport for private sectorProvide fodder for affected stockFlexible taxation systems for
affected people
Drought contingency planning allow for implementation of :
Mitigation
Relief
Rehabilitation
Drought contingency planning for implementation:
Overall drought policy, setting out plans objectives of minimizing the impact of drought
Set plans for specific mitigation, relief and rehabilitation measures
Construction of dams and additional reservoirs for supply of water.
Cloud seeding- artificial rain
Desalination of sea water for irrigation or consumption.
Drought monitoring by total rainfall levels and total usage levels
Land use by carefully planned crop rotation
Outdoor water use restrictionRainwater harvestingRecycled waterRelief worksDisease prevention and control
• Contingency planning done by Govt. Policy issues, national, regional and
district level rural development infrastructure input supply, marketing and farm
advisory services• Non- Govt.NGO’SRural institutionsPrivate sectors
Augmentation of water
It includes methods for providing an entirely new supply of fresh water and techniques for increasing utility of available supplies of water.
New supply of water include weather modification.
Weather modification done to increase precipitation and decrease Evapotranspiration.
Cloud seeding done to increase precipitation.
Available water supplies increased by conservation of available water supplies.
Agricultural water requirements can be reduced by reducing conveyance losses, and discouraging wasteful irrigation techniques.
Technique should be developed to reduce water consumption in home and industry.
Evaporation losses from small reservoirs can be reduced by providing roofs.
Reclamation and reuse of waste water can be encouraged.
Evaporation loss in ground water is less. Use of ground water storage reservoir in conjunction with surface storage reservoirs.
Infiltration losses can be reduced by sealing the soil surface useful in arid regions.
Water harvesting done by collecting from roof top, pavements, constructing small storage.
Measures for water conservation
Goals of water conservation efforts include:
Sustainability- ensure availability for future generations
Energy conservation- world 15% energy production dependent on water management.
Habitat conservation- preserve fresh water habitat, migrating waterfowl.
Benefits of water conservation:
Save water save money.Reduction in excess water use
reduce waste water generation, reduce overflowing of gutter.
Ecosystem and habitat protection.Helps in improving quality of
drinking water.
Water conservation measures by:
Domestic conservation
Industrial conservation
Agricultural conservation
Domestic conservation
Repair all leaks quicklyTurn off water when not in useUse conserving appliance which use
low volume water for domestic useLocal bodies should install water
meter and encourage water pricing.
Industrial conservation
Use cooling system which use less water.
Reuse of cooling water for irrigation or other purposes.
Install in plant treatment measures for treating the waste water or effluent.
Agricultural (irrigation) conservation
Improved irrigation methods such as sprinklers or drip irrigation.
Water required for agricultural considerably reduced by reducing conveyance loss.
Evaporation losses from small reservoirs can be reduced by providing roofs over them.
Use of lined canals which reduce seepage and evaporation.
Use of ground water storage reservoir in conjunction with modern surface storage reservoirs to reduce evaporation loss, in arid regions.
Price agricultural water to encourage conservation.
Infiltration losses reduced by sealing soil surface.
Water harvesting in arid regions.
For conservation of water the following structures can be constructed:
Earthen bundGully pluggingCheck damKhet talawadi
Earthen bund
Gully plugging
Check dam
Khet Talawadi
Water harvestingCollection of rain water called water
harvesting.Rainwater harvesting is
accumulation and storing of rainwater for reuse, before it reaches aquifer.
Water collected from roofs of houses, schools, local institutions make important contribution.
Water collected from ground, called storm water harvesting.
Benefits of rainwater harvesting
Increase water availabilityChecks declining water tableEnvironmental friendlyImproves water quality of ground
waterSurface water runoff conservationPrevents soil erosion and flooding in
urban area
Rainwater harvesting technique
Rainwater collection – Roof top rainwater harvesting
Runoff collection – Surface runoff harvesting
Recharge to ground waterRunoff enhancement
Roof top rain water harvesting
Rainwater captured from roof catchments and stored in sub surface ground water reservoir.
Objective is to make water available for future use.
Useful in dry land, hilly, urban and costal areas.
Components of roof top rainwater harvesting
a collection area a conveyance system storage facility a delivery system
Storage reservoir expensive part, careful design and construction required.
First rainwater should be flushed or diverted.
Surface runoff harvesting
Surface runoff harvesting is traditional technique.
Small dams, ponds, tanks are used.
Used for irrigation, domestic, livestock use.
Small damsSmall dams/check dams constructed
in natural channel to impound the runoff water up to certain depth.
Impounded water slowly infiltrate into soil and recharge ground water.
Ponds and reservoirsImpounding type and dug-cut type
ponds constructed.In impounding type, a retaining wall
or dam is constructed to block the flow of water in a natural storm.
In dug-cut type area is excavated to store the runoff.
Reservoirs requires water storage area, spillways and earth embankment.
Storage tankSurface or above ground tankSubsurface or underground tankStorage tanks requireSolid secure coverCoarse inlet filterOverflow pipeManhole, sump and drain to
facilitate cleaningOutlet system, tap or pump
Recharge to ground waterThe structures generally used:PitsTrenchesDug wellHand pumpsRecharge wellSpreading techniquesUnderground reservoirs
Runoff enhancement Can be done by increase
precipitation.Seeding generally done to increase
precipitation.Precipitation can be increased by
10% by cloud seeding.Lumb demonstrated that increase in
annual runoff (∆R) due to small increase in precipitation (∆P) is given by∆R= ∆P (0.29+1.2 R/P)
R= mean runoff, P= mean precipitation
Methods for runoff enhancement:Cloud seedingEnhancement by paved surfaces.Surface of drainage basin effect on
runoff. Bare surface give more runoff.
Drainage basin located on windward side of mountain produce more runoff.
Runoff affected by geology of drainage basin. Pervious soil yield less runoff.
Drainage basin has larger no of natural depressions, which deposited by other material then runoff at basin increases.
More Human activity, more load on soil, reduce infiltration, hence increase runoff.
ASSIGNMENT
1. Discuss various causes of drought2. Discuss drought contingency
planning and its importance.3. Explain augmentation of water and
its various methods.4. Explain water conservation and its
various methods.5. Discuss importance of rainwater
harvesting and explain various techniques used for it.