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element of civil engg. WATER RESOURCES

element of civil engg. WATER RESOURCES

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    Water education ppt Water education ppt Presentation Transcript

    • Hydrology The flow of water across and through near surface environments
    • Precipitation • Single strongest variable driving hydrologic processes • Formed by water vapor in the atmosphere • As air cools its ability to ‘hold’ water decreases and some turns to liquid or ice (snow)
    • Causes of Precipitation
    • • Weather (day to day) vs. climate (years-decades and patterns) • What are hydrologists most concerned with? • Climate and geography result in biome classification Weather vs. Climate Patterns
    • Biomes and Rainfall
    • Moisture Sources for USA
    • Fig. 4.1 Evaporation & Transpiration
    • Fig. 4.4
    • Plant Transpiration Most water absorption occurs in upper half of root zone
    • Annual Pan Evaporation in USA
    • Evaporating playa lake with salts around margin, eastern Washington
    • WaterFlow Hillslope Hydrology Runoff Processes: Horton overland flow Subsurface stormflow, Return flow Groundwater flow
    • Factors Affecting Water Movement in Soils
    • As we discuss mechanisms, remember… – Many processes occur simultaneously – Shifts can occur between processes in space and time – Antecedent wetness conditions are important – Watershed characteristic play a central role Runoff Generation
    • Horton overland flow occurs when the rainfall intensity exceeds the infiltration capacity Horton Overland Flow
    • Once thought to be the ONLY mechanism of runoff generation Became coded into hydrologic models still in use today Subsequent work showed role of partial source area where Saturation overland flow is produced Horton Overland Flow
    • If rainfall exceeds soil infiltration capacity: – Water fills surface depression then – Water spills over downslope as overland flow and – Eventually to the stream Horton Overland Flow
    • Subsurface Stormflow Lateral flow through soil above conductivity contrast. Consists of both slower matrix flow and faster macropore flow
    • Macropore flow, Tennessee Valley, California
    • Saturation Overland Flow Direct rainfall onto saturated areas. Return flow from saturated soils in topographic lows and along valley bottoms where water table rises to intersect the surface.
    • Overland flow, Tennessee Valley, California
    • Overland flow, Tennessee Valley, California
    • Generally a minor contribution to runoff, why? Direct Precipitation on Channels
    • Groundwater & the Vadose Zone
    • Groundwater Flow Driven by hydraulic gradients Q = K I A K is hydraulic conductivity A is cross sectional area I is hydraulic gradient
    • Hydrographs by Runoff Mechanism Lag to peak Throughflow SOF HOF Peak Runoff HOF SOF Throughflow
    • Water balance of drainage basins Net difference between precipitation and evaporation yields streamflow or groundwater recharge
    • Gaining and Losing Streams
    • Watershed Urbanization
    • MS
    • Dams Dam is a solid barrier constructed at a suitable location across a river valley to store flowing water. Storage of water is utilized for following objectives:  Hydropower  Irrigation  Water for domestic consumption  For drought and flood control  Other additional utilization is to develop fisheries.
    • Structure of dam
    • Arch Dam  This type of dams are concrete dams which are curved or convex upstream in plan  This shape helps to transmits the major part of the worlds loads to the abutments  Arch dams are built across narrow deep river gorges But now in recent years they have been considered even for little wider valleys.
    •  Earth dams are trapezoidal in shape  Earth dams are constructed where the foundation rocks are weak to support  Earth dams are relatively smaller in height and broad at the base  They are mainly built with clay , sand and gravel. hence they are also known as Earth Fill dam or Rock Fill dam Earth dam
    • o Buttress Dam - Is a gravity dam reinforced by structural supports o Buttress Dam –A support that transmits a force from a roof or wall to another supporting structure Buttress Dam This type of structure can be considered even if the foundation rocks are little weaker
    • Gravity Dam These dams are heavy and massive wall-like structure of concrete in which the whole weight acts vertically downwards
    • Bhakra Dam  Bhakra dam is the highest concrete gravity dam in asia and 2nd highest in the world  This dam is present across the river Sutlej in himachal Pradesh  About construction it was started in the year 1948,completed in 1963 Details: About measurements 740 ft high from the deepest foundation as straight concrete dam being more than 3 times the height of Qutub Minar.
    • Leakages Below dams takes place generally due to the weak planes or zones occurring at the dam sites The reservoirs,which lies in the upstream side(when full),contain an enormous plenty of water due to great extent, on downward side of the dam,the water level wil be very low.due to this difference in levels,the reservoir water attempts to leak through the rocks of dam with considerable pressure and emerge in the downstream side
    • Dams are very costly projects,so their construction in seismic areas needs careful study to ensure their safety.when earth quakes occurs,a dam is subjected to two forces are due to the dam and due to reservoir water. conclusion
    • The Water Cycle
    • Water never leaves the Earth. It is constantly being cycled through the atmosphere, ocean, and land. This process, known as the water cycle, is driven by energy from the sun. The water cycle is crucial to the existence of life on our planet.
    • The Water Cycle
    • During part of the water cycle, the sun heats up liquid water and changes it to a gas by the process of evaporation. Water that evaporates from Earth’s oceans, lakes, rivers, and moist soil rises up into the atmosphere.
    • The process of evaporation from plants is called transpiration. (In other words, it’s like plants sweating.)
    • As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds.
    • When the water in the clouds gets too heavy, the water falls back to the earth. This is called precipitation.
    • When rain falls on the land, some of the water is absorbed into the ground forming pockets of water called groundwater. Most groundwater eventually returns to the ocean. Other precipitation runs directly into streams or rivers. Water that collects in rivers, streams, and oceans is called runoff.
    • The Hydrological Cycle Higher Geography The Hydrosphere
    • The Hydrological Cycle What you need to know: Be able to draw a diagram of the hydrological cycle. Describe its main elements. Explain how balance is maintained within the system.
    • What is the Hydrological Cycle? The hydrological cycle is the system which describes the distribution and movement of water between the earth and its atmosphere. The model involves the continual circulation of water between the oceans, the atmosphere, vegetation and land.
    • The Hydrological cycle
    • Describing the Cycle: • Evaporation Solar energy powers the cycle. Heat energy from the sun causes evaporation from water surfaces (rivers, lakes and oceans) and….
    • • … transpiration from plants. Transpiration is essentially evaporation of water from plant leaves. • Evapotranspiration – water loss to the atmosphere from plants and water surfaces.
    • Condensation  The warm, moist air (containing water vapour) rises and, as it cools, condensation takes place to form clouds.
    • Advection • Wind energy may move clouds over land surfaces where …
    • Precipitation • …precipitation occurs, either as rain or snow depending on altitude.
    • • Stemflow (red arrows) – Precipitation flows down stems and branches to ground • Throughflow (yellow) Rate at which precipitation flows through branches
    • Run off / Overland flow • The rainwater flows, either over the ground (run off) into rivers and back to the ocean, or…
    • Groundwater flow • … infiltrates downwards through the soil and rocks where it is returned to the oceans through groundwater flow.
    • Groundwater flow
    • Hydrological Cycle Bingo Also called the hydrological cycle Split your page into 8 squares and write one word from the list below in the each square Condensation Ground Water Infiltration Evaporation Precipitation Percolation Run off Evapotranspiration Interception Saturation The Hydrological Cycle The water table
    • The water cycle balance  Usually the water cycle is in balance, and the amount of precipitation falling will slowly soak into the ground and eventually reach the rivers.  However, if rain falls for a long period of time or if the ground is already soaked or saturated with water then the chance of flooding is increased.
    • Under the ground
    • A closed system  The hydrological cycle is a good example of a closed system: the total amount of water is the same, with virtually no water added to or lost from the cycle.  Water just moves from one storage type to another.  Water evaporating from the oceans is balanced by water being returned through precipitation and surface run off.
    • Your Turn Write down the meaning of the following words: • Infiltrate • Groundwater flow • Surface runoff • Evapotranspiration • Closed system Use the New Higher Geography Textbook p.10 to help you. Then complete Activity 1 (a) – (c)
    • Human Inputs to the Cycle  Although this is a closed system there is a natural balance maintained between the exchange of water within the system  Human activities have the potential to lead to changes in this balance which will have knock on impacts.  For example as the earth warms due to global warming the rate of exchange in the cycle (between land and sea and atmosphere) is expected to increase.
    • Human Inputs  Some aspects of the hydrologic cycle can be utilized by humans for a direct economic benefit  Example: generation of electricity (hydroelectric power stations and reservoirs)  These are effectively huge artificial lakes and this will disrupt river hydrology (amount of water in a river)
    • Other Human Activities • Paving, compacting soils, and altering the nature of the vegetation (including deforestation) • The mining of ground water for use in agriculture and industry • Large amounts of water vapour released into the atmosphere from industrial activity • Large changes in vegetation by wildfire, logging, clearance for agriculture
    • Impacts • These human activities can lead to increase chances of flooding • Increases in soil erosion • A cooling effect on the north west of Europe (climate change) • Possible higher precipitation levels in the Arctic but less in the Tropics
    • Watershed development
    • Watershed development Watershed area mainly has three types of land use 1.Forest area Nonarable land 2.Pasture land 3.Arable land
    • In arable land soil and water conservation structures: 1.Bunding 2.Water ways 3.Farm pond 4.Loose boulders 5.Waste weir
    • Soil and water conservation structures between nonarable land: 1. Diversion drain 2. Nallah bund 3. Check dam
    • Peak run off rate estimation by Rational formula Q= CIA/360 Q =Peak runoff (Cu.m/sec) C=Runoff Coefficient (Weighted mean) I = Design Intensity of rainfall (mm/hr) for the design frequency and for duration equal to the time of concentration. A = Catchment area (Hectares)
    • Table of Runoff coefficient value(C)
    • Runoff Coefficient (C): weighted value of “C” =(A1C1 + A2 C2 + A3C3+ ……+AnCn) / (A1+A2+A3+….+An) To calculate I (design rainfall intensity) I = 2xIo / 1+Tc where, Tc = time of concentration Kirpitch formula , Tc = 0.01947x( k): · ⁷⁷ where, k = √(Lᶟ/H) L= length of nallah H= level difference Iᶟ = rainfall intensity in mm/hr
    • Map for calculation of Iᶟ
    • Type of structure Recurrence interval 1. Earthen structure like bunds, terraces , waterways, diversion drains, and dry stone works 10 years 2. Semi permanent masonary structures like small check dams , waste weir etc. 25 years 3. Permanent structures made of cement concrete and RCC and other large structures 50 years
    • PROBLEM: calculate the discharge of a watershed having area 120ha out of that 20ha is forest area having 11% slope and sandy loam soil condition ,10ha pasture land with 7% slope having silty loam soil and the remaining 90ha is under cultivated land with only 3%slope under clay soil the major nala length is 800m &level diff. from farthest point to end point is 50m the watershed is located an 16 ° latitude &76 ° longitude type of structure is a small check dam. Solution: Runoff coefficient(C) from table : c for forest area =0.30 c for pasture area =0.36 c for argil. Area =0.60 weighted value of C=0.3x20+0.36x10+0.6x90/120 =0.53
    • Design intensity(I) = 2Iᶟ/1+Tc Where Tc = 0.01947×{√(Lᶟ/H)} : · ⁷⁷ = 0.01947 × {√(800ᶟ/50)} : · ⁷⁷ = 9.73min = 0.162hrs Iᶟ = 60 mm/hr from rainfall intensity map for16° latitude &76 ° longitude for 25 years R.I. So, I= 2 ×60/(1+0.162) = 103.44 mm/hr From Rational formula , Q = CIA/360 =0.53×103.44×120/360 =18.27 cum/s
    • Check dam Check dams mainly classified as: 1. Temporary check dams, Ex.:- loose boulders 2. Permanent check dams, Ex.:- drop spillway Check dams are used for controlling the soil erosion and runoff in small and medium sized gullies. Components of check dam:- Head wall, head wall extension, side wall, apron, wing wall, weir, end sill, cut off wall, toe wall
    • Check dam in netranahalli watershed Length of weir
    • Dam height and weir height in check dam Dam height Weir height Head wall extension
    • Head wall extension of check dam Head wall extension
    • Length of apron of check dam Length of apron Side wall
    • End wall of check dam End wall
    • Design of check dam 1. Peak rate of runoff, Q= CIA/360 2. Q for rectangular weir = 1.71LH³′² where, L= length of weir = width of nala, m H= height of weir , m From this we can find H because L and Q is known. total height of weir = H+ free board Free board is 0.15 to 0.30m
    • 3. Height of dam,D = nala height-weir height 4. Head wall extension = 2H+0.3 5. Length of apron = 2D 6. Height of wing wall and side wall = 2H 7. Wall thickness, head wall = 0.45m side wall= 0.3m wing wall=0.3m
    • Problem(cont.) : design a rectangular weir from the data given in previous problem and following data: Catchment area = 120 hac, Nallah width = 15m . Calculate head wall extension, length of apron, dam height for 3.5 m nala depth. Solution: from above problem Q= 18027 cumec Q for rectangular weir = 1.71LH³′² 18.27 = 1.71 * 15 * H³′² H = 0.71 m add free board(.29) , H = .71+.29 = 1.0 m Head wall extension = 2H+0.3 = 2.3m Height of dam, D = nala height – weir height = 3.5 – 1 =2.5m Length of apron = 2D = 2* 2.5 = 5 m
    • Diversion drain Diversion drain is excavated to intercept the runoff from the area situated above (nonarable land) for protecting arable lands down below and to conduct it safely to natural nalas. Design of diversion drain 1. calculate total area (nonarable) in hectares . 2. Use rational formula, discharge Q=CIA/360 for 10 years frequency .
    • Diversion drain Upstream side downstream bermTop width Side slope
    • Diversion drain in Ramsagara watershed
    • 3. Q =VA area of cross-section , A= (b+zd)d where, b=bottom width , m d=depth of drain, m z=side slope top width of drain , T = b+2dz velocity of flow , V by manning’s formula = C R2/3 S1/2 where, C= 1/n , n= manning’s roughness coefficient R= hydraulic radius = A/P ,m
    • P= wetted perimeter , m = b+ 2d {√(z²+1)} S= grade of diversion drain (0.2 to 0.3 %) V should be in between 2 – 6 m/s 4. Length of drain = perimeter of hillock , m 5. Depth of diversion drain is assumed as a) d = 0.5 to 1 m in rough terrains . b) d = 1.5 to 2 m in marginal terrains. 6. Construct stabilizers(local stones) to reduce velocity when fall of bed slope is >30 cm. 7. Excavated earth is put on D/S with leaving a berm of 0.6m and vegetative barriers on U/S side
    • • Problem :- Calculate the peak discharge and design the diversion drain in forest land having catchment area 30 ha and sandy soil . I =90mm/hr ,slope of land 20% using modified ‘C’ value. Solution: Q=CIA/360 Q=0.2x90x30/360 1 1.5 1 1 Q= 1.5 cumec assume V = 0.6m/sec non erosive velocity Q =VA 1:1 1.5=0.6A A=2.5 sqm A=(b+zd)d where, b=bottom width d=depth 1.5 2.5=(b+zd)d (assume d=1) 2.5=(b+1)1 2.5-1=b b=1.5m T = b+2dz = 1.5+2*1*1 = 3.5m
    • Problem : calculate the discharge and Design diversion drain from above problem data by using ‘C’ value from the table. Solution: C = 0.3 from table Q=CIA/360 Q=0.3x90x30/360 = 2.25 cumec assume V = 0.6 m/sec non erosive velocity Q = AV A = Q/V = 2.25/0.6 = 3.75 m² Now , A = (b+zd)d assume d = 1m 3.75 = (b+1)1 b = 2.75 m T = 2.75 + 2*1*1 = 4.75m
    • Farm pond it is a water harvesting/storage structure in arable land. Types:- 1. Embankment type. 2. Dug out type. Embankment type pond is built across the stream in areas of gentle to moderately slope. Dug out type pond are constructed by excavating the soil , relatively in level areas.
    • Farm pond Depth gauging scale
    • Inlet of farm pond INLET
    • Outlet of farm pond OUTLET Stop dam
    • Design of dug out type farm pond 1. Calculate the runoff volume(V1) from catchment area(A). V1=A × d where, d= runoff depth i.e. some % of rainfall. 2. Calculate design runoff volume(V) i.e. some % of total runoff volume(V1). 3. Side slope(z:1) of farm pond:- (A) for red soil= 1.5:1 (B) for black soil= 2:1
    • 4. Depth(d) of farm pond can be assumed according to farm pond capacity, it should not more than 3m. 5. Bottom width(b)= b= √(3V - d3Z2) - dz √ 3d 6. Top width (T) = b+2dz 7. Capacity of farm pond can be determined by trapezoidal rule V = (A₁+A₂)×H/2 where , A₁ and A₂ are areas b/w 2 successive contours H = vertical interval of contours 8. Volume of excavation for construction of pond by prismodial formula V = (A+4B+C)*D/6 9. Design of inlet and outlet such as mechanical and emergency spillway.
    • Problem : design a farm pond in red soil region from the following information : catchment area = 5ha, mean annual rainfall = 450mm runoff = 10% of total mean annual rainfall, assume 50% of runoff collection for design , side slope can be assured 1.5:1 solution: 10% of annual rainfall = 450 x 0.10 = 45 mm total runoff volume for 45 mm from 5ha = 45/1000 x 5 x10000 =2250 cubic m design runoff volume (v) = 50% of total runoff volume = 0.50 x 2250 = 1125 cubic m then , b= √(3v - d3z2) - dz √3d
    • b = Bottom width V = Volume = 1125 mᶟ Z = Side slope = 1.5 assume d= Depth = 2.5m b= √ (3 x1125 – 2.5ᶟx 1.5²) – 2.5x1.5 √ 3 x2.5 = 21.10–3.75 = 17.35m Top width = T = b +2dz = 17.35 + 2 x 2.5 x 1.5 = 24.85m
    • Bunding  It is a soil conservation measure , used for retaining the water , creating obstruction and thus to control erosion. Bunds are embankment type structures, constructed across the slope. By bunding practice entire area is divided into several small parts, there by effective slope length, thus reducing soil erosion.
    • Types of Bund: 1. CONTOUR BUND: • constructed on contour of area. • used in relatively low rainfall (<600mm/year) area for the purpose of controlling soil erosion and to store rain water. • Suitable for land having slope of 2 to 6%. • Black soil is not suitable for contour bund.
    • Contour bund Contour bund
    • Bund with borrow pits, waste weir and revetment
    • 2. GRADED BUND: • When a grade is provided to bund is called GB. • Constructed in relatively medium to high RF(>700mm/year). • Suitable for black soil. • Purpose of controlling soil erosion and to store rain water. • Suitable for land having slope of 2 to 6%.
    • Specification of contour bund Soil Type Land Slope (%) VI (m) Common Cross section (Sqm) Side slope Surplussing arrangement Deep black Upto 3 0.9 1.61 1.5:1 Waste weir Shallow black Upto 3 1.0 1.0 to 1.5 1.5:1 Waste weir Red and Lateritic Upto 3 0.5 1.0 to 1.5 1.3:1or 1.5:1 Open ends with vegetative checks
    • Typical spacing of contour bund Slope % VI (m) (S/3 + 2 ) 0.3 HI (m) VI/Slope % X 100 Length of Bunds (m) (10,000)/HI 1.0% 0.70 70 145 1.5% 0.75 50 200 2.0% 0.80 40 250 2.5% 0.85 35 205 3.0% 0.90 30 335
    • Design of contour bund 1. Spacing of bund by formula a) Ramser’s formula VI = (S/3+2)0.3 b) USDA formula VI = (S/4+2)0.3 c) Cox formula VI = (XS+Y)0.3 where, X= rainfall factors Y= infiltration and crop cover factor
    • Values of X and Y for Cox formula Rainfall Annual rainfall (cm) Value of X Intake Crop cover during erosive period of rains Y values Scanty 64 0.8 Below average Low coverage 1.0 Moderate 64-90 0.6 Average or above Good coverage 2.0 Heavy >90 0.4 One of above favorable & Other unfavourable Good coverage 1.5 Value of X Y values
    • 2. Horizontal interval (HI) = (VI/slope) x 100 3. Rainfall excess (Re) = Rainfall x % runoff 100 (Rainfall of 24 hrs, 10 yr. recurrence interval) 4. Depth of impounding (h)= (VI x Re)/50 5. Depth of temporary storage = 0.3 m 6. Free board (25% inclusive of settlement allowance) = 0. 25 (h+0.3)m 7. Total height of the bund = h + 0.25 (h +0. 3) m.
    • Select top width and slope of bund depending on soil type Type of the soil Top width (m) side slope Sandy 0.5 2:1 Loamy 0.4 1.5:1 Clayey 0.3 1:1 or 1.5:1
    • 9. Computation of the bottom width and cross section area ‘A’ 10. Total length of bund/ha L = 10,000 x 1. 3 HI 30% extra length of soil bunds. 11. Earthwork in bunding/ ha V = L X A V= Volume of bund, cum per ha L= Length of bund, m per ha A= C/S area of bund, sqm
    • Specification of graded bund Soil Type Slope (%) VI (m) Cross Section (Sqm) Side slope grade Black Upto 5 0.75 to 1.0 0.6 to 0.87 1.5:1 0.1 to 0.3 Red Upto 5 0.75 to 1.0 0.6 to 0.87 1.3:1 0.2 to 0.4 Lateritic 5 to 6 0.75 to 1.5 0.34 to 0.56 1.3:1 0.2 to 0.4
    • • Steps in design of graded bund are similar to that of contour bund.
    • Waste weir (WW) • WW(surplus weirs)or rubble/grass outlets are normally provided in valley points by using loose stones properly embedded in soil to avoid scouring and to drain the excess water accumulated against bund. • WW are constructed when catchment area is <40 hac. • For larger catchment areas, water diversion is necessary. • constructed in series from ridge to valley.
    • Waste weir Upstream side Downstream side Length
    • Specification of waste weir  width is equal to width of waterway.  crest height in black soils= 15 to 20 cm in red soils = 30 to 40 cm  upstream slope = 1.5:1  down stream slope =3:1  whenever open ends are used for draining excess water; the ends are to be vegetated to prevent cutting and scouring.  2m long murram or hard soil packing may be given to either ends of WW in continuation of bund.
    • Gabion structure • gabion is a ‘Italic’ word in which small-small stones combined with G.I. wire mesh, to form a large stone and placed across the nala to control heavy flow there by silt. • this structure is comparatively strong under both compression and tensile strength.
    • Gabion structure in Netranahalli watershed Length of gabion width
    • Gabion structure with vegetative barriers to reduce runoff velocity Vegetative barriersgabion
    • Technical specification 1. G.I wire 10-14 gauge 2. Foundation = 0.3m 3. Height above ground = 0.70 m 4. Length inside nala = 1 m at both sides 5. Total Length of gabion = width of nala+2m 6. Wire mesh size = 3 inch so, stones should be >3 inch size 7. Spacing for 1-3% slope = 50 m for 3-5% slope = 30 m
    • • Gabion should be constructed maximum in a 2 m box and join them, filled with stones and tie them together. • Bigger stones should be in the bottom and smaller stones (not < 3inch) at the top. • Binding should be proper.
    • Contour trenching • Contour Trench/’V’ ditches are trenches dug on contour in non-arable lands of more than 3% slope to hold run off for conservation and reducing erosion. • They are established for development of trees and grass species and are adoptable in areas with annual rainfall of up to 950 mm. • contour trenches have been used on all slopes, trenching on slopes exceeding 20% is not advisable either technically or economically.
    • Trenches are categorized in 3 types 1.Continuous trenches: Continuous contour trenches are recommended for storage of water in low rainfall relatively flat areas receiving storms of mild intensity. 2. Graded trenches These are drainage type ditches for intercepting and safe disposal of surface flow in very high rainfall areas and impermeable black soils. • The grade is given so that the intercepted runoff from the above will be carried safely at non- erosive velocity to the vertical drain without overflow.
    • 3. Staggered or interrupted trenches In high rainfall areas with highly dissected topography staggered trenches are usually adopted. Staggered trenches are of shorter lengths in a row and are arranged along the contour with inter space between them.
    • Earthen dam for water harvesting (NALABUND) Nala bund is an earthen structure constructed across the nala/gully in order to store the runoff water flowing through the nala during rainy season. Objectives: • reducing the velocity of flow, • storing the runoff and thereby allowing it to percolate into the soil profile which in turn helps to enhance the water table of the downstream area. • This structure also prevents the silt flowing down and causing the siltation of reservoirs in the downstream side, which can affect the storage capacity of the reservoir.
    • Site selection of nala bund 1.First and foremost requirement is that it should have sufficient catchment to fetch the runoff required for storage. 2. The upstream side of the location there should have enough area for water storage. 3. The nala site selected for the structure should have a relatively narrow cross section. 4. Should be located on the straight stretch of nala. 5. There should be provision for locating surplussing weir on one of the banks. 6. The nala bed should have good hard soil for proper bondage between the structure and natural soil profile. A hard rock foundation may have less bondage with the proposed structure, hence discouraged.
    • Nala bund
    • Design of nala bund 1. Top width, W = Z/5 +3 Where: W= width of crest (m), Z=Height of embankment above the stream bed(m). 2.EMBANKMENT SIDE SLOPES: The side slope of the nala bund depends primarily on stability of the material used for embankment.
    • Recommended side slopes for earthen embankment
    • 3.CORE WALL: The core wall is a centrally provided fairly impervious wall in the dam. 4. KEY TRENCH: This is a bondage/foundation component of the structure to ensure the stability for the embankment almost like foundation of a structure. 5. Spillway : This is a vent /channel provided at the full tank level in order to dispose of the excess runoff coming in. 6.FREE BOARD: Free board is the additional height of the bund provided to avoid water overtopping the embankment during unexpected flow of runoff 7.REVETMENT (wave protection): Since this an earthen structure and it will be coming in contact with the water in the upstream side of the dam, in order to with stand against the wave action of storage .
    • forestry
    • Forest for conservation of natural resources • Forest: An area set aside for the production of timber and other produce or maintain under woody vegetation. Theory and practice and creation Conservation Scientific management of forest Utilization of their resources
    • Conservation forestry • Production of forest product • Restoration & maintenances of resource base
    • Conservation forestry Its need & scope At the global level 15% of the earth’s forest & woodland disappeared during the last one and half century as a result of human activities. Its aim is to prevent erosion from the fertile agricultural land as well as production as socially acceptable uses.
    • The role of forest in functioning of watershed Conserves soil moisture Maintain soil temperature Infiltration increases Root binding capacity increases Prevent soil erosion
    • Objective of agroforestry To utilize available farm resource. Production of fuel, fodder, food, wood etc. Integration of trees with agricultural land and animal production. To maintain ecological balance. To check erosion hazard. To improve employment potential and rural economy.
    • Extension
    • Pra (participatory rural apprisal • The PRA technique is an useful technique for use in analysis of any situation STEPS Social Mapping Resource Mapping Seasonal analysis Transect walk Preference ranking Historical time line ITK
    • CONSERVATION AGRONAMY
    • In situ soil &moisture conservation measures • Tillage a)Conservation tillage b)Conventional tillage • Graded furrow • Vegetative barriers • Repeated inter culturing • Graded border strips • Zing terrace • Contour cultivation • Compartmental bunding • Tied ridges & furrows • Broad furrow & ridges • Scooping • Border planting method
    • Effect of in situ moisture conservation on soil physical properties • Soil temperature • Bulk density • Penetration resistance • Soil compaction • Soil aggregation & pore space • Runoff & soil loss • Nutrient losses • Crop growth & yield
    • Definition & concept of Water shed management • Watershed is the integration of technologies with in the natural boundaries of drainage area for optimum development of land , water, & plant resources to meet the basic needs of people & animal in sustainable manner.
    • Components of watershed management • Treatment of arable & non arable land for effective in situ & ex situ moisture conservation • Identification of sound crop production system & its implementation through development & input agencies • Developing suitable infra structure facilities & people organizations to maintain developed resources
    • Soil science
    • The systematic arrangement of land into various categories according to its capability to sustain particular land use without land degradation. LAND CAPABILITY CLASSIFICATION
    • OBJECTIVES OF LCC • It makes available the technical data contained in a soil survey map in a simple & practical language • Indicates the hazards of soil erosion • Indicates the most intensive , profitable & safe use of any piece of land
    • Land capability groups • Land suitable for cultivation and other uses (Class I to IV lands) • Land not suitable for agriculture but well suited for forestry, grass land and wild life (Class V to VIII)
    • Influence of effective soil depth on LCC
    • Influence of soil texture on LCC
    • Influence of slope on LCC
    • Influence of erosion on LCC
    • Influence of climate on LCC
    • Determination of bulk density, particle density and pore space Readings taken from soil samples in lab: Sl no. Weight of soil taken , W(gm) Volume of soil taken, V1 (ml) Volume of water added, V2(ml) Volume of soil+water Volume of soil+water at end of exp V3(ml) 1. 30 23.5 50 72.5 59.5 2. 30 20.5 50 70.5 62.5
    • calculation 1. Pore space volume(V4) = (V1+V2)-V3 V4 = 23.5+50-59.5= 14ml % pore space = V4/V1*100 = 14/23.5*100 = 59.57% bulk density = weight of soil/volume of soil = 30/23.5 = 1.27 gm/cc Particle density = weight of soil/(V1-V4) = 30/(23.5- 14 ) = 3.157 gm/cc
    • 2. Pore space volume(V4) = (V1+V2)-V3 = 20.5+50-62.5 = 8ml %pore space = = V4/V1*100 = 8/20.5*100 = 39.02% bulk density = weight of soil/volume of soil = 30/20.5= 1.46 gm/cc Particle density = weight of soil/(V1-V4) = 30/(20.5-8) = 2.4 gm/cc
    • Sources of water (RAIN) Surface Sources Ground Sources Streams Springs Lakes Infiltration Galleries Ponds Infiltration Wells Rivers Wells and Tube wells Impounded Reservoirs Oceans
    • Springs •Natural outflow of GW @ earth’s surface. •Gravity springs : GW table rises high & water overflows though the sides of a natural valley or depression. •Surface springs : an impervious obstruction supporting underground storages becomes inclined causing water table to go up & get exposed to ground surface. •Artesian Springs : when water flowing through some confined aquifer is under pressure.
    • Artesian spring
    • Aquifers & Aquicludes
    • Non artesian or Unconfined aquifers & well
    • Wells •A water well is a hole usually vertical, excavated in the earth to bring GW to the surface. •Open Wells / Tube Wells.
    • Open Wells (Dug Wells) •Open masonry wells, 2 – 9 m dia, less than 20 m depth. Discharge 5 L/s •Walls built of brick or stone masonry or precast concrete ring •To improve yield of well, 10 cm dia hole @ centre of well is made (Shallow well/Deep Wells) •Shallow well rests in a pervious strata. •Deep well rests on an impervious ‘mota’ layer & draws its supply from the pervious formation lying below ‘mota’ layer. •A shallow well might be having more depth than a deep well
    • Deep wells
    • Infiltration Galleries (Horizontal Wells) •Horizontal tunnels (with holes on sides) constructed of masonry walls with roof slabs to tap GW flowing towards rivers/lake. •Constructed @ shallow depths (3-5m) along the banks of river either axially along or across GW flow. •Width (1m), depth (2m) , length (10 – 100m) •If large GW quantity exists, porous drain pipes are provided and they are surrounded by gravel and broken stone. •Yield, 15,000 L/day / Meter length •A collecting well @ shore end of gallery serves as sump from where water is pumped.
    • Section of infiltration gallery
    • Infiltration galleries
    • •They are shallow wells constructed under beds of rivers. •Deposits of sand exist at least 3m deep in river beds. As the water percolates down, impurities are removed. Quality of water is better than river water. •They are sunk in series in the bank of the river. •They are closed @ top & open & bottom. Manholes are provided @ top for inspection. •They are constructed of brick basonry with open joints. •Various infiltration wells are connected by porous pipes to sump called jack well. Infiltration Wells
    • •Structures used to withdraw water from various sources. •Lake / Reservoir / River /Canal/ Intake. Intakes
    • •Submersible intake. •A pipe laid in the bed of the lake. •One end is in the middle of the lake & is fitted with bell – mouth opening covered with a mesh & protected by concrete crib. •Water enters in the pipe through bell-mouth opening & flows under gravity to the bank where it is collected in a sump – well & then pumped to TP. Lake Intakes
    • •A circular masonry tower (4-7m dia) constructed along bank of the river. •Water enters in the lower portion of the intake (i/e sump – well) from penstocks. •Penstocks are fitted with screens to prevent entry of floating solids. • No. of penstock openings are provided in intake to admit water @ different levels. •Opening & closing of penstock valves is done with wheels provided @ pump – house floor. River Intakes
    • • Constructed inside river @ suitable place. •A concrete circular shell filled with water upto water level inside the river. •Water enters through openings provided on outer circular shell, as well as on inside shell. •Water is taken to the bank of the river through the withdrawal conduit in the sump well from where it is pumped to WTP. a) Wet Intakes
    • b)Dry Intake tower •In wet intake tower, water enters first in the outer shell then it enters in the inner shell. •In dry intake, water enters directly withdrawal conduit.
    • •An intake tower constructed on the slope of the dam. •Intake pipes are fixed @ different level to withdraw water at all variations of water level. •All inlet pipes are connected to one vertical pipe inside the intake well. •Screens are provided @ mouth of all intake pipes to prevent entry of floating matter. •Water entering the vertical pipes is taken to other side of the dam by means of an outlet pipe. Reservoir Intake
    • •At the top of intake tower, sluice valves are provided to control flow of water. •Valve tower is connected to the top of the dam by means of foot- bridge gang- way. •For earthen dams, intake towers are separately constructed. •For RCC masonry dams, intake tower is constructed inside the dam it self.
    • Reservoir Intake tower
    • Canal Intake •No need to provide multiple ports, as water level in canal remains constant. •A pipe placed in a brick masonry chamber constructed partly in the canal bank. •On one side of chamber, opening is provided with coarse screen for entrance of water. •A bell mouth fitted with a hemispherical fine screen is provided @ the mouth of the pipe. •Outlet pipe carries water to the other side of the canal bank from where it is taken to TP. •One sluice valve operated by a wheel from top of masonry chamber is provided to control flow of water in the pipe.
    • Canal intake well
    • Dry intake tower standing in the river or reservoir
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    • THANK U 1 AND ALL