Hydrology

HYDROLOGYCIEN 3183ENGR. MARICON LOURDES G. CONCEPCION -REBAYAFirst Grading:(ME) Midterm Examination(CS) Class Standing(MG) Midterm Grade = 1/3 (ME) + 2/3 (CS)

Second Grading:(FE) Final Examination(CS) Class Standing(SG) Second Grade = 1/3 (FE) + 2/3 (CS)

Final Grade = (ME + SG) / 2GRADING SYSTEMEngineering Hydrologyby: K. Subramanya

Hydrology for Engineersby: Ray K. Linsley, et. al.

Hydrology and Floodplain Analysisby: Philip B. Bedient, et. al.REFERENCESRunoffDefinition of RunoffPortions of RunoffRunoff ProcessSurface RunoffChannel RunoffFactors Affecting RunoffRunoff CycleConditions of Runoff CycleSummary of Rainfall Runoff CycleTOPICS FOR REPORTINGGroup 1:Groundwater HydrologyGround WaterSubsurface ZonesWater TableIntersticesPorosityPermeability

Group 2:Water Yielding PropertiesSpecific Yield and Specific RetentionDarcys LawCoefficient of PermeabilityPermeability vs. Hydraulic ConductivityApplicability of Darcys LawHomogeneity / HeterogeneityIsotropy / AnisotropyCombinationsSteady State vs. Transient FlowTransmissivity (or Coefficient of Transmissibility)Storativity (or Storage Coefficient)

TOPICS FOR REPORTINGGroup 3:Ground Water ReservoirGeologic FormationsAquifersAquifer SustainabilityGround Water FlowTypes of Aquifers

Group 4:Well HydraulicsWellsDetermination of Discharge from Open WellsConstruction of Open WellsTube WellsMain Parts of a Tube WellTypes of Tube Wells

GROUPINGS

Water Yielding PropertiesSpecific Yield and Specific RetentionDarcys LawCoefficient of PermeabilityPermeability vs. Hydraulic ConductivityApplicability of Darcys LawHomogeneity / HeterogeneityIsotropy / AnisotropyCombinationsSteady State vs. Transient FlowTransmissivity (or Coefficient of Transmissibility)Storativity (or Storage Coefficient)TOPICS FOR REPORTINGGround Water ReservoirGeologic FormationsAquifersAquifer SustainabilityGround Water FlowTypes of AquifersTOPICS FOR REPORTINGWell HydraulicsWellsDetermination of Discharge from Open WellsConstruction of Open WellsTube WellsMain Parts of a Tube WellTypes of Tube WellsTOPICS FOR REPORTINGWater is the most abundant substance on earth, the principal constituent of all the living things, and a major force constantly shaping the surface of the earth.

It is also a key factor in air-conditioning the earth for human existence and in influencing the progress of civilization.

Hydrology, which treats all phases of the earths water, is a subject of great importance for people and their environment.IntroductionHydrology treats of the waters of the Earth, their occurrence, circulation, and distribution, their chemical and physical properties, and their reaction with their environment, including their relation to living things.

The domain of hydrology embraces the full life history of water on the Earth. Engineering hydrology includes those segments of the field pertinent to planning, design, and operation of engineering projects for the control and use of water.Definition of HydrologyHydrology is a multidisciplinary subject that deals with the occurrence, circulation, and distribution of the waters of the Earth.

The domain of hydrology embraces the physical, chemical, and biological reactions of water in natural and man-made environments.

Because of the complex nature of the hydrologic cycle and its relation to weather patterns, soil types, and other geologic factors, the boundaries between hydrology and other earth sciences such as meteorology, geology, ecology and oceanography are not distinct.Definition of HydrologyHydrology is the study of the movement, distribution, and quality of water throughout the Earth, including the hydrologic cycle, water resources and environmental watershed sustainability.Definition of HydrologyHydrology is used in engineering mainly in connection with the design and operation of hydraulic structures. These are the typical questions that the hydrologist is expected to answer:

What flood flows can be expected over a spillway, at a highway culvert, or in an urban storm drainage system?What reservoir capacity is required to assure adequate water for irrigation of municipal water supply during droughts?What effect will reservoirs, levees, and other control works exert on flood flows in a stream?What are reasonable boundaries for the floodplain? Hydrology in EngineeringDesign and operations of hydraulic structures Water supplyWastewater treatment and disposalIrrigationDrainageHydropower generationApplication of HydrologyFlood controlNavigationErosion and sediment controlSalinity controlPollution abatementRecreational use of waterFish and wildlife protectionApplication of Hydrology

Hydrologic CycleThe hydrologic cycle is a continuous process in which water is evaporated from the oceans, moves inland as moist air masses, and produces precipitation if the correct conditions exist.

The precipitation that falls on the land surface is dispersed via several pathways. A portion of the precipitation, or rainfall, is retained in the soil near where it falls and returns to the atmosphere by evaporation, the conversion of water to water vapor, and transpiration, the loss of water vapor through plant tissue.

The combined loss, called evapotranspiration, is a maximum value if the water supply in the soil is adequate at all times.Hydrologic CycleAnother portion becomes overland inflow or direct runoff, which feeds local streams and rivers. Finally, some water enters the soil system as infiltration and may reenter channels later as interflow or may percolate to the deeper ground water system.

Surface and ground water move toward lower elevations and may eventually discharge into the ocean.

However, large quantities of surface water and portions of ground water may return to the atmosphere by evaporation and evapotranspiration.Hydrologic CyclePrecipitation:Rainfall. Condensed water vapor that falls to the Earth's surface

Evaporation:The conversion of water to water vapor. The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere.

Transpiration:The loss of water vapor through plant tissue. The release of water vapor from plants and soil into the air. Water vapor is a gas that cannot be seen.Hydrologic Cycle - SummaryEvapotranspiration:Combined loss

Runoff:The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

Infiltration:Water enters the soil and may reenter channels later as interflow or may percolate to the deeper ground water system. The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.Hydrologic Cycle - SummaryThe world's total volume of water is in many different forms:

Liquid- oceans, rivers and rainSolid- glaciersGas- invisible water vapor in the air

Water changes states as it is moved around the planet by wind currents.Understanding the Water CycleWater ResourcesFresh water3%Saline (Oceans)97%Earths waterGroundwater30.1%Icecaps and Glaciers68.7%Surface water0.3%Others0.9%FreshwaterLakes87%Swamps11%Rivers2%Fresh surface waterSources of Natural Drinking Wateris water in a river,lakeor fresh waterwetland. Surface water is naturallyis fresh water located in theporespace of soil androckswater that is flowing within aquifersbelow thewater tableis precipitation that is collected from relatively clean, above-ground surfaces - usually rooftops. is water that has the property of salinity and temperature which controls the density of the water. In hydrology, a water balance equation can be used to describe the flow of water in and out of a system.

A system can be one of several hydrological domains, such as a column of soil or a drainage basin.

Water balance can also refer to the ways in which an organism maintains water in dry or hot conditions. It is often discussed in reference to plants or arthropods, which have a variety of water retention mechanisms, including a lipid waxy coating that has limited permeability.Water BalanceFor any hydrologic system, a water budget can be developed to account for various flow pathways and storage components. The simplest system is an impervious inclined plane, confined on all four sides with a single outlet. A small urban parking lot follows such a model. The hydrologic continuity equation for any system is:

where,I=inflow, vol/timeO=outflow, vol/timedS/dt=change in storage, vol/timeWater Balance

A general water balance equation is:

P = R + ET + G + Swhere,P = precipitationR = surface runoffG = ground water flow or InfiltrationE = evaporationT = transpirationS = change in storageWater BalanceAs rainfall accumulates on the surface, the surface detention increases and eventually becomes outflow from the system.

Neglecting evaporation for the period of, but delayed somewhat in time.

The difference between accumulated inflow and outflow at any time represents the change in storage.

The same concept can be applied to small basins or large watershed, with the added difficulty that all loss terms in the hydrologic budget may not be known.Water BalanceA watershed is defined as an area of land that drains to a single outlet and is separated from other watersheds by a watershed divide.Water Balance

For a given time period, a conceptual mathematical model of the overall budget for the hydrologic cycle would become, in units of depth (in or cm) over the basin.

P R G E T = S

where,P = precipitationR = surface runoffG = ground water flowE = evaporationT = transpirationS = change in storageWater BalanceA runoff coefficient can be defined as the ratio R/P. Note that infiltration I is the loss from the surface system and a gain to the ground water and thus cancels out of the overall budget.

Also, the units of inches (or cm) represents a volume of water when multiplied by the surface area of the watershed.Water BalanceExample:

In a given year, a watershed with an area of 2,500 km2 received 130 cm of precipitation. The average rate of flow measured in a river draining the watershed was 30m3/s. Estimate the amount of water lost due to the combined effects of evaporation, transpiration, and infiltration to ground water. How much runoff reached the river for the year (in cm)? What is the runoff coefficient? Assume that water levels are the same throughout the year, thus, no change in storage.Water BalanceSolution:Problem 1:

Given:A = 2,500 km2P = 130 cmR = 30 m3/sS = 0t = 1 yearET+G = ?Water BalanceSolution:

I O = SP R ET G = SR = (30 m3/s)(86,400 s/day)(365 day/yr)(100 cm/m)(1 yr) (2500 km2)(1000 m/km) 2R = 37.90 cm

ET+G = 130 cm 37.90 cm = 92.1 cm

Runoff Coefficient:

R/P = 37.90 / 130R/P = 0.29Water BalanceExample:

A lake with a surface area of 525 acres was monitored over a period of time. During a one-month period, the inflow was 30 cfs, the outflow was 27 cfs, and a 1.5 inch seepage loss measured. During the same month, the total precipitation was 4.25 inches. Evaporation loss was estimated as 6.0 inches. Estimate the storage change for this lake during the month.Water BalanceSolution:Problem 2:

Given:A = 525 acrest = 1 monthI = 30 ft3/sO = 27 ft3/sS = 1.5 inches

P = 4.25 inchesE = 6.0 inchesS = ?Water BalanceSheet1I-O=dSdt