Hydro Logical Models

8/2/2019 Hydro Logical Models

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Introduction Principles of Model Formulation

Classification of Hydrological Models Applications GIS and Hydrology Examples Conclusions


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A hydrological model is the mathematical

representation of the flow of water and itsconstituents on the land surface orsubsurface environment.

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Weather generating processes

Water resources

Terrestrial hydrologic cycle: many coupled

processes


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Hydrologic Budget (In Out = Storage)

Watershed

Precipitation (P)Groundwater in (GWin)

Evaporation (E)

Transpiration (T) Streamflow (Q)

Groundwater out (GWou

Reservoir

Infiltration (I)

(P + GWin) (E + T + I + GWout + Q) = Storagereservoir


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Other key variables: soils

type and association

derived characteristics geology

type derived characteristics

land use vegetation cover management practices

artificial drainage storm drains/sewers

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Atmospheric Model

Land Surface Model

Groundwater/Vadose Model

Surface Water


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Land surface model

Overland flow

Land surface model

Overland flow

Regional climate model

Moisture/heat flux

Evapotranspiration

Infiltration/Seepage

Precipitation/Advectio

Runoff/Routing


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Parsimony: no morecomplex than needed;smallest number of

parameters; valuesobtained from data

Modesty: do not pretendto do too much

Accuracy: accuracies ofmodel and measurementsshould match

Testability: valid or not

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Functionality, ease of use

Datarequire

ments

modelcomplexity

Spatial characteristics ....


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Statistical models include consideration ofuncertainties in both the parameters and inputdata.

Deterministic simulation models describe thebehavior of the hydrologic processes in awatershed using mathematical expressions that

interrelate the various phases of the hydrologiccycle.


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Lumped: A lumpedhydrologic model takes noaccount of spatial

variability in parametersdescribing the watershed,the hydrologic processes,the input data or theboundary conditions.


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Distributed models account for spatialvariability of hydrologic processes, input

data, boundary conditions, and watershedcharacteristics.

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Event-simulation models as used for modeling asingle event like precipitation runoff event. Theygenerally use time intervals on the order of hours or

even minutes. Continuous models are generally used to model

flow over longer periods of time such as months and

even years accounting for all the precipitation-runoff events during the period.

S ti l h t i ti


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Control and mitigation of pollution in surface- andground water

Use of water for domestic supply, agriculture andindustry, under consideration of ecologicalimpacts

Flood control and mitigation

Scientific insight / Predictive tool for management

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Spatial characteristics ....


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Groundwater model

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The hydraulic models are used to calculatewater stage, or water-surface profiles along a

river or channel.

They can also be used to determine areasinundated by flood discharges and to studythe effects on floodplains.

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Soil erosion within a river system is bound todecrease the usefulness of regulated

reservoirs and is therefore important tomaster by suitable measures. Existing methods to predict the useful

lifetime of a reservoir is to assess thetransport of suspended load by the river andassume that this load will settle in thereservoir.

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One dimensional models describing a columnbased on the groundwater surface and

reaching up to some few meters in theatmosphere. The models involve more or less

sophisticated descriptions of vegetation. The soil description can be more or less

detailed and a few models also allow fortreatment of soil frost.

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Hydro-chemical models allow prediction ofthe chemical states with land use practices as

part of the input to soil, streams, rivers andlakes. The models can simulate use of both

fertilizers and manure, from which plantstake nitrogen in various rates.

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Despite of many advances due to GISapplication,

in many cases, the use of GIS forhydrological modelling led to compromisesand misuse due to conceptualincompatibilities between the fundamentalassumptions in GIS and hydrological models.

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Conclusion

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Hydro Logical Models