| Harvesting Water |
| Rainwater Run off |
| Geology, Ground water, India |
| Ground water Recharge |
| Rainwater Harvesting methods |
| Contact |
| Calculation Methodology |
| Times of concentration |
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for overland flow may be calculated using the methodology
presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as
amended or replaced from time to time by NRCS) for developed sites.
Times of concentration for channel and pipe flow shall be computed using the Manning
equation.
Times of concentration for undeveloped sites
may be computed using the SCS equation for Tag Time: |
| Artificial Recharge |
| FORMAT FOR PREPARATION OF ARTIFICIAL RECHARGE PROJECT
Base Information of Problem Area
1. Location State District Block Basin/Sub Basin/Watershed Lat. & Longitude Area Extent 2. Population (i) Human - Urban & Rural Livestock 3. Land use (i) Cultivable & Non-cultivable Area Forest 4. Agriculture (i) Soil Type, thickness and extent (ii) Cropping Pattern (iii) Area under irrigation (a) Surface water (b) Ground water 5. Climate (i) Type of Climate (a) Humid (b) Sub-Humid (c) Arid (d) Semi-arid (ii) Rainfall (a) Average annual (b) Rainfall Distribution (c) No. of Rainy days (d) Temperature (e) Humidity (f) P.E.T. (g) Wind 6. Topographic Features (i) Elevation range (Maximum, Minimum) (ii) Landform (a) Hilly Area (b) Dissected plateau (c) Foot Hill Zone (d) Piedmont Zone (e) Valley Slopes (f) Plain Area (g) Sand dune Area (h) Delta Region (i) Coastal Plains (j) Karstitic Terrain 7. Surface Water Bodies: (i) Rivers/Streams - Perennial, Ephemera (ii) Average Discharge & Duration of flow (iii) Canal - Lined / Unlined (iv)Length and capacity of canal and duration of canal flow (v) Number and Area of Natural Lake & ponds. (vi)Reservoirs, their number and storage capacity (a) major (b) Medium (c) Minor. 8. Hydrogeology (i) Geological Formations (ii) Major Rock Types (iii) Structural Features (iv)Nature of unsaturated zone (a) Moisture conditions (b) Presence/Absence of impervious Layers in vadose zone (v) Aquifer systems; Phreatic (b) Semi-confined(c) Confined (vi) Depth of Aquifer Zones (vii) Hydraulic Characteristics of Aquifers: (a) Transmissivity (b) Storativity /Specific yield (c) Hydraulic Conductivity (viii) Aquifer boundaries (ix) Depth of Water level and its seasonal fluctuation. (x) Ground Water Structures (a) Type, Number (b) Depth range (c) Yield range (d) Aquifer tapped (xi) Ground Water Resources (a) Annual Recharge (b) Annual Draft (c) Stage of Ground Water Development (xii) Ground Water Level trends. 9. Water Requirements (i) Present requirement for different uses (Domestic, Industrial and Irrigation). (ii) Projected requirement after 10 years, 20 years (Domestic, Industrial and Irrigation) 10. Ground Water (i) Unconfined & confined aquifers (a) Potable (b) Brackish (c) Saline (ii) Any special quality problem, (Seawater intrusion, pollution, high fluoride etc.). 11. Nature of problem requiring (i) Quantity Problem Artificial Recharge of Ground Water (a) Quantification of Water shortage for different purposes. (b) Period of Shortage (c) Location of deficit areas. (ii) Quantity Problem (a) Control of Sea Water Intrusion 12. Source Water Availability For Artificial Recharge Purpose- Rainfall, Rivers, Canals, Mun.corp. 13. Sub-surface Potential for (i) Thickness of un-saturated zone Ground Water Recharge. (below 3 mbgl). (ii) Total runoff in the catchment (iii) Committed flow….. (iv) Surplus available for recharge. B. Guidelines for Action Plan 1. Identify the data gaps in base information and carry out necessary investigations using the various investigation techniques. 2. Using base data on topography, rainfall, hydrogeology, aquifer situation land source water availability, identify the methods which may be suitable. 3. With reference to the local conditions of the area, further identify the most appropriate techniques of artificial recharge suitable at various sites/locations. 4. Determine the number of each type of artificial recharge structure needed to achieve the quantitative targets. 5. For individual structure at different locations, finalize the design specifications. 6. Finalize the design of the conveyance system required to bring the source water to the recharge site and the treatment required. 7. Plan the required Monitoring System to evaluate the efficiency of Recharge Scheme. 8. Evaluate the economic feasibility of the Artificial Recharge Project. ( CGWB, New Delhi, May 2000) |
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| Ground Water Recharge (Infiltration/Recharge/Retention) |
| The ability to retain and maximize the ground water recharge capacity of the area being developed or redeveloped is encouraged. Design of the infiltration/recharge stormwater management facilities shall give consideration to providing ground water recharge to compensate for the reduction in the percolation that occurs when the ground surface is paved and roofed over. These measures are encouraged, particularly in hydrologic soil groups A and B, and shall be utilized wherever feasible.
1. Percent Volume Method Rev = [(S)(Rv)(A)]/12 where: Rev = Ground Water Recharge Volume (ac-ft) S = Soil Specific Recharge Factor Rv = 0.05 + 0.009(I), I = Percent Impervious Cover (i.e. use I=20 when there is 20% impervious cover) A = Site Area (acres)* *Note: Drainage areas having no impervious cover and no proposed disturbance during development may be excluded from the Rev calculations (i.e. the Site Area (A) may be reduced). Designers are encouraged to use these areas as non-structural practices for Rev treatment. 2. Percent Area Method Rev = (S)(Ai) where: Rev = Ground Water Recharge Volume (ac-ft) S = Soil Specific Recharge Factor Ai = Measured Impervious Cover (acres) Hydrologic Soil Group (HSG) Soil Specific Recharge Factor (S) The recharge volume is considered part of the total WQv that must be provided at a site and can be achieved either by a structural practice (e.g., infiltration, bioretention), a non-structural practice (e.g., buffers, disconnection of rooftops) or combination of both. Note: Rev and WQv are inclusive. When treated separately, the Rev may be subtracted from the WQv when sizing the water quality BMP. ASR and ASTR Aquifer Storage and Recovery (ASR) For the Aquifer Storage and Recovery (ASR) a well, bore well or shaft is used for both injection and recovery of water. ASR has become one of the most popular and commonly used deep well recharge techniques. In many cases, the storage zones are aquifers that have experienced long-term declines in water levels due to heavy pumping to meet increasing urban and agricultural water needs. Groundwater levels can then be restored if adequate volumes of water are recharged. Aquifer Storage Transfer and Recovery (ASTR) Aquifer Storage Transfer and Recovery (ASTR) involves water injection through a borehole, and recovery from another, some distance away, to increase travel time and benefit from the water treatment capacity of the aquifer. Suspended Solids and Clogging Problem: A major requirement for waters that are to be used in recharge projects is that they be silt-free. Silt may be defined as the content of undissolved solid matter, usually measured in mg/l, which settles in stagnant water with velocities which do not exceed 0.1 m/hr. To obtain still clearer water, with only 10 - 12 mg/l suspended solids, further additions of flocculants and, frequently, agitation of the water must be resorted to. First, near the surface the interstices of the soil may be filled up and a layer of mud may be deposited on the surface, on the other hand suspended particles may penetrate deeper into the soil and accumulate there. Methods to minimize the clogging effect by suspended matter can be classified into broad groups: a) Periodical removing of the mud-cake and dicing or scraping of the surface layer. b) Installation of a filter on the surface, the permeability of which is lower than that of the natural strata (the filter must, of course, be removed and renewed periodically) c) Addition of organic matter or chemicals to the uppermost layer. d) Cultivation of certain plant-covers, notably certain kinds of grass. Providing inverted filter consisting of fine sand coarse sand and gravel at the bottom of infiltration pits/trenches are very effective. Clogging by biological activity depends upon the mineralogical and organic composition of the water and basin floor and upon the grain-size and permeability of the floor. The only feasible method of treatment developed so far consists in thoroughly drying the ground under the basin. Vertical Recharge Shaft - The vertical recharge shaft can be further improvised with injection well at the bottom of the shaft. (a) Without Injection well • Ideally suited for deep water levels (up to 15 metres b.g.l.) • Presence of clay is encountered within 15 m. • Effective in the areas of less vertical natural recharge • Copious water available can be effectively recharged. • Effective with silt water also (using inverted filter consisting of layers of sand, gravel and boulder) • Depth and diameter depends upon the depth of aquifer and volume of water to be recharged. • The rate of recharge depends on the aquifer material and silt content in the water. (b) With Injection Well In this technique at the bottom of recharge shaft a injection well of 100 - 150 mm diameter is constructed piercing through the layers of impermeable horizon to the potential aquifers to be reached about 3 to 5 meter below the water level . • Ideally suitable for very deep water levels (more than 15 meters) • Aquifer is over lain by impervious thick clay beds • Injection well can be with or without assembly • The injection well with assembly should have screen in the potential aquifer at least 3 – 5 meter below the water level. • The injection well without assembly is filled with gravel to provide hydraulic continuity so that water is directly recharged into the aquifer • The injection well without assembly is very cost effective. • Depending upon volume of water to be injected, number of injection wells, can be increased to enhance the recharge rate. • The efficiency is very high and rate of recharge goes even up. Lateral Recharge Shaft • Ideally suited for areas where permeable sandy horizon is within 3 meter below ground level and continues upto the water level - under unconfined conditions • Copious water available can be easily recharged due to large storage and recharge potential. • Silt water can be easily recharged • 2 to 3 meter wide and 2 to 3 meter deep trench is excavated, length of which depends on the volume of water to be handled. • With and without injection well |
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