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HYDROGEOLOGY- GEOHYDROLOGY

Hydrogeology ( hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers).

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HYDROGEOLOGY- GEOHYDROLOGY

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  1. Hydrogeology (hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers). Hydrogeology, according to the Oxford English Dictionary, refers to the study of water at or below the earth's surface. Those who study it are hydrogeologists. Geo-hydrology a science that deals with the character, source, and mode of occurrence of underground water. Geohydrology, according to the Merriam-Webster Dictionary, only deals with water that is below the earth's surface. Those who study it are geohydrologists. HYDROGEOLOGY- GEOHYDROLOGY

  2. Characteristics of rainfall that affect the amount and rate of runoff are: • intensity • depth • distribution over an area (spatial) • distribution over time (temporal). Characteristics of rainfall that affect the amount and rate of runoff are: • intensity • depth • distribution over an area (spatial) • distribution over time (temporal). • rainfall characteristics • catchment characteristics.

  3. Rainfall -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)

  4. Values of Parameters for Intensity – Duration - Return Period Relationships This relationship is known as Intensity – Duration – Frequency (IDF) relationship and can be expressed in the form of a formula or in the form of a graphic curve. Such a relationship can be developed by conducting an analysis of past rainfall records for this area under study.

  5. subtitle Hydrology.........an Introduction to Groundwater & Surface Water

  6. Evapotranspiration: The loss water from the soil through both evaporation and transpiration from plants.Infiltration - The downward entry of water into the immediate surface of soil or other materials Percolation -Vertical and Lateral Movement of water through the soil by gravity. Recharge: Groundwater supplies are replenished, or recharged, when water enters the saturation zone by actions like rain or snow melt. Surface runoff: Water above the surface of the land, including lakes, rivers, streams, ponds, floodwater, and runoff. Interflow, the water that infiltrates the soil surface and travels by means of gravity toward a stream channel (always above the main groundwater level) and eventually empties into the channel. Groundwater flow is defined as the "...part of stream flow that has infiltrated the ground, has entered the phreatic zone.

  7. Factors Affecting Water Movement in Soils

  8. Surface Water – starts with Infiltration capacity (how much rain can ground absorb before water runs off) determines what land will look like LOW – water runs off HIGH –water sinks in

  9. INFILTRATION Infiltration is the term applied to the process of water entry into the soil. Infiltration Capacity- The maximum rate at which water can infiltrate into a soil under a given set of conditions. Infiltration Rate- The rate at which water penetrates the surface of the soil and expressed in cm/hr, mm/hr, or inches/hr. The rate of infiltration is limited by the capacity of the soil and rate at which water is applied to the surface. This is a volume flux of water flowing into the profile per unit of soil surface area (expressed as velocity). If the rate of infiltration is limiting, the entire water balance in the root zone will be affected.

  10. Water at various depths

  11. Natural Recharge

  12. NATURAL GROUND WATER RECHARGE ESTIMATION IN INDIA Chaturvedi FormulaBased on the water level fluctuation and rainfall amounts (when rainfall exceeds 40cms). R = 2.0 (P - 15)*0.4 where, R = net recharge due to precipitation during the year, in inches P = annual precipitation, in inches UP Irrigation Research Institute, Roorkee, formula is, R = 1.35 (P-14)*0.5 Amritsar formula ( rainfall between 60 and 70 cms. ) R = 2.5 (P - 0.6)* 0.5 where, R & P both are measured in inches Krishna Rao Formula R = K (P - X) The following relation is stated to hold good for different parts of Karnataka; R = 0.20 (P - 400) for areas with P between 400 and 600mm R = 0.25 (P - 400) for areas with P between 600 and 1000mm R = 0.35 (P - 600) for areas with P above 2000mm where, R & P are expressed in millimeters

  13. Drainage Divide separates basins

  14. Policies need to be different for different types of drainage basins

  15. Tributary – patterns as a result of Geology Dendritic same rock type Radial Volcano Out from Center Rectangular Jointed & faulted Trellis Big stream cuts across anticline folds

  16. Introduction to Groundwater The zone of saturation occurs where water completely fills the open spaces in the soil and rock. The upper limit of this zone is called the water table. The zone above the water table is called the zone of aeration.

  17. How water gets into the zone of saturation (well water)

  18. Soil Formation • FACTORS AFFECTING SOIL FORMATION • Parent Materials (resistance, composition) • Climate (precipitation, temperature) • Biota (vegetation, microbes, soil fauna) • Topography (slope, aspect, hillslope position) • Time (period since parent material exposed)

  19. SOIL HORIZONS Partially decomposed organic material dominates Good mix of mineral and organic particles (mainly mineral) ELUVIATION E Horizon may be present Silicate clays, iron oxides, aluminium oxides, and calcium carbonates accumulate (little organic matter) ILLUVIATION Least weathered part of the soil profile The exposed wall of a soil pit or road cut is called the soil profile Regolith (above bedrock) May be transported (ie., can be distinct from parent material) http://www.physicalgeography.net

  20. Topsoil • The organically-enriched A horizon at the soil surface • in a cultivated soil • Most nutrient-rich portion of cultivated soils • Contains the majority of plant roots • Subsoil • The soils that underlie the topsoil • Lower in most nutrients • Drainage properties important in determining • susceptibility to waterlogging and soil moisture stress

  21. SUITABLE SOILS Particle Size Distribution

  22. Porosity and Permeability Porosity: volume proportion made up of voids Permeability: connectedness of voids, dictating capacity to transmit flow

  23. WATER MOVEMENT & SOIL STRUCTURE

  24. Typical relationship between specific yield, specific retention, and total porosity for different soil types

  25. Rock A rock is an assemblage of minerals bound together • Igneous (solidify and crystallize from molten magma) • Sedimentary (settling) • Metamorphic (altered under pressure)

  26. The Rock Cycle

  27. Igneous Structures Flows Veins Dikes and Sills Chilled or baked margins Magmatic flow foliation Flow tops marked by vesicles Aa-aa vs. pahoehoe structure Stocks and batholiths Xenoliths or inclusions Magmatic segregations

  28. Sedimentary Structures • Bedding • Uncomformities • Cross bedding • Graded bedding • Ripple marks • Mud cracks

  29. Secondary Geologic Structuresdevelop after formation of the rock body • Folds • Fractures and joints • Faults and breccias • Foliation and lineation • Metamorphic fabrics like contact metamorphic aureoles and mylonitic S-C structures

  30. Ground Water Movement in rocks • Movement of ground water through pores and fractures is relatively slow (cms to meters/day) compared to flow of water in surface streams • Flow velocities in cavernous limestones can be much higher (kms/day) • Flow velocity depends upon: • Slopeof the water table • Permeability of the rock or sediment

  31. Aquifers and Aquitards • Aquifer - body of saturated rock or sediment through which water can move easily • Sandstone • Conglomerate • Well-jointed limestone • Highly fractured rock • Aquitard - rock/sediment that retards ground water flow due to low porosity and/or permeability • Shale, clay, unfractured crystalline rocks

  32. Unconfined Aquifer • Unconfined Aquifer • Has a water table, and is only partly filled with water • Rapidly recharged by precipitation infiltrating down to the saturated zone

  33. Confined Aquifers • Confined Aquifer • Completely filled with water under pressure (hydrostatic head) • Separated from surface by impermeable confining layer/aquitard • Very slowly recharged

  34. Wells • Well - a deep hole dug or drilled into the ground to obtain water from an aquifer • Wells in unconfined aquifers, water level before pumping is the water table • Water enters well from pore spaces within the surrounding aquifer creating a cone of depression • Water table can be lowered by pumping, a process known as drawdown Insert new Fig. 11.8 here

  35. Material saturated with water lies below the water table. Materials that conduct water (are porous and permeable) are aquifers. Materials that do not conduct water (are well-cemented, unfractured, etc.) are aquicludes & aquitards. The Water Table One inch of rain on one acre of ground results in 27,192 gallons of water (~100,000 L).

  36. Groundwater returns to surfaceas baseflow to streams (in humid areas)

  37. Groundwater: aquifers must be permeable and porous • Any geologic unit through which water can move easily (i.e. it’s permeable) • Porosity: how much water a geologic material can hold

  38. Typical Values of Infiltration Rates

  39. Zones of underground water

  40. Example Layered Aquifer System Bedient et al., 1999.

  41. Hydraulic Conductivity K • K represents a measure of the ability for flow through porous media: • K is highest for gravels - 0.1 to 1 cm/sec • K is high for sands - 10-2 to 10-3 cm/sec • K is moderate for silts - 10-4 to 10-5 cm/sec • K is lowest for clays - 10-7 to 10-9 cm/sec

  42. Groundwater Flow Q = K I A K is hydraulic conductivity A is cross sectional area I is hydraulic gradient

  43. Before Rain After Rain & water moves to streams

  44. THE HOLY WATER OF ZAM ZAM According to Arab historians, the Zamzam Well, except for a few periods when it became dry or was buried under sand, has been in use for around 4000 years. Structure and hydrogeology of the Well The Zamzam Well is hand-excavated and is about 30.5 m deep, with an internal diameter ranging from 1.08 to 2.66 m. Hydrogeologically, the well lies within Wadi Ibrahim, which runs through the Holy City of Makkah, and taps groundwater from the wadi alluvium and, to a much lesser extent, the underlying fresh bedrock. The upper 13.5 m of the well is excavated in the sandy alluvium of the Wadi Ibrahim, and the lower 17.0 m in the underlying diorite bedrock. In between lies a 0.5 m thick highly permeable weathered rock. Most of the alluvial section of the well is lined with stone masonry except for the uppermost 1m, which has a reinforced concrete collar.. The weathered rock section is lined with stone and it is this section that provides the main water entry into the well.

  45. Research issues and objectives • Zamzam Studies and Research Center at SGS is to provide the required scientific solutions for effective monitoring and management of the aquifer feeding the Zamzam well and to ensure the purity and security of supply. The Center is currently focusing on the following aspects of management of the aquifer, the well and the Zamzam supply and distribution system: • Monitoring and managing demand to prevent depletion, • Urbanization of the Wadi Ibrahim catchment and its effect on recharge, • Management of storm drainage in relation to recharge, • Maintaining groundwater movement and quality through building controls, • Upgrading of the Zamzam pumping and storage system, • Optimization of Zamzam supply and distribution,

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