DPHM-RS (Semi-Distributed Physically based Hydrologic Model using Remote Sensing and GIS) is a semi-distributed hydrologic model developed at

University of Alberta The University of Alberta, also known as U of A or UAlberta, is a public research university located in Edmonton, Alberta, Canada. It was founded in 1908 by Alexander Cameron Rutherford,"A Gentleman of Strathcona – Alexander Cameron Ruth ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

Model description

The semi-distributed DPHM-RS (Semi-Distributed Physically based Hydrologic Model using Remote Sensing and GIS) sub-divides a

river basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the ...

to a number of sub-basins, computes the

evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpir ...

soil moisture Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that ent ...

and

surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the ...

using energy and rainfall forcing data in a sub-basin scale. It consists of six basic components: interception of

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

, evapotranspiration, soil moisture, saturated subsurface flow, surface flow and channel routing, as described in Biftu and Gan. The interception of

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...

from the

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. ...

by the canopy is modeled using the Rutter Interception Model. The land surface evaporation and

vegetation Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic charact ...

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth ...

are computed separately using the Two Source Model of Shuttleworth and Gurney, which is based on the energy balance above canopy, within canopy and at soil surface. This model solves the non-linear equations based on the energy balance for the canopy, surface, and air temperatures at canopy height, evaporation from soil surface and transpiration from vegetation. A soil profile of three homogeneous layers (active, transmission and saturated layers) is used to model the soil moisture on the basis of water balance between layers. The active layer is 15–30 cm thick and it simulates the rapid changes of soil moisture content under high frequency atmospheric forcing. The transmission zone lies between the base of the active layer and the top of the

capillary fringe The capillary fringe is the subsurface layer in which groundwater seeps up from a water table by capillary action to fill pores. Pores at the base of the capillary fringe are filled with water due to tension saturation. This saturated portion of t ...

and so it more characterizes the seasonal (instead of transient) changes of soil moisture. In modeling the unsaturated flow component of soil water, the water transport is assumed vertical and non-interactive between sub-basins. The lower boundary of the unsaturated zone is the top of capillary fringe controlled by the local average ground water table derived from the catchment average

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. Th ...

and topographic soil index which include the spatial variability of the topographic and soil parameters. Starting with an observed value from the surrounding wells of the modeled basin, the temporal changes in the average ground water depth is based on the water balance analysis for the whole catchment, and the rate of change of the average ground water table is assumed to be the rate of change of local water table. After simulating the soil moisture, the saturation and Hortonian infiltration excess for vegetated and bare soil are computed to generate the surface runoff for each sub-basin.

Philip's equation Philips is a multinational Dutch electronics corporation. Philips may also refer to: * Philips (family) of the Dutch-Jewish electronics corporation * Philips (surname) * Philips Classics Records, the classical music division of Philips Records * ...

is used to compute the infiltration capacity of soil, and the surface runoff is distributed temporally using a

time lag response function Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

obtained from a reference rainfall excess of 1 cm depth applied to each grid cell within the sub-basin for one time step. Then for each grid cell, which has the resolution of the

digital elevation model A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid. A "global DEM" refers to a discre ...

(DEM) used, the flow is routed according to the kinematic wave equation from cell to cell based on eight possible flow directions until the total runoff water for the sub-basin is completely routed. The resulting runoff becomes a lateral inflow to the stream channel within the sub-basin and these flows are routed through the drainage network by the Muskingum-Cunge routing method whose variable parameters are evaluated by an iterative four point approach.Ponce, V.M., and Yevjevich, V., 1978. Muskingum-Cunge method for variable parameters. Proc. ASCE 104(HY12).

References

{{Reflist Hydrology

Model description

See also

References