Hydrograph model is a distributed process-based model of runoff formation processes



01.05.2015
Вторые Виноградовские Чтения. Искусство гидрологии
Прием регистрационных форм и тезисов докладов открыт на сайте конференции до 15 июня 2015 г.

26.06.2014
First Lower Yenisei Observatory Network workshop, summer 2015, Krasnoyarsk - Igarka
Pre-workshop flyers in Russian and English are attached

13.12.2013
15th ERB Conference “Advances in Hydrologic Research on Pristine, Rural and Urban Small Basins” September 9-13, 2014
will be held in Portugal. The flyer of the conference is attached.

 

  Hydrograph model is a distributed process-based model of runoff formation processes.

 

 

The main advantages of the model are the following:

  1. It may be used in any climate and landscape zone.
  2. It is free of a scale problem: the model can be applied for process simulations from soil profle to giant watersheds without change of its sctructure.
  3. Most of the parameters are physical properties of the watersheds which may be observed in nature. Parameters do not need much calibration and can be ported from one watershed to another with similar conditions.

 

It describes all components of the land hydrological cycle, including: precipitation and its interception; snow accumulation and melt; evaporation from snow, soil and vegetation cover; surface flow and infiltration; soil water dynamics and flow; heat dynamics and phase change in soil layers; underground flow formation, slope and channel flow transformation; and flow discharge. It is designed to be applied in any geographical area of the Earth.

 

The model forcing data consist of the standard and most simple meteorological information from observational networks that can be obtained even for data scarce regions; these include daily values of air temperature, moisture deficit, and precipitation.

 

The various outputs of the model are the continuous runoff hydrographs at the outlet, from any part of the basin or a specified landscape; the distributed state variables, reflecting water and heat dynamics in soil layers and snow cover; spatial and temporal distribution of water balance elements including precipitation; evaporation from snow, soil and vegetation cover; surface, subsurface and underground runoff.

 

 

 

 

Discretization of the watershed

 

In the horizontal dimensions, the model divides the watershed into a number of Representative Points (RP). Also in the horizontal dimensions, the watershed is divided into the runoff formation complexes, or RFCs which are assumed to be homogeneous for soils, vegetation, topography, hydrology, etc. and which may cover from a fraction of an RP to several RPs.

 

In the vertical direction, the model represents the soil column with at least 3 strata (usually, up to 10-15), for which energy and water balance are computed, and whose physical properties (model parameters) are arranged by RFCs. In addition, the model considers 15 layers for the deeper ground water flows, for which only the water balance is computed.

 

The parameters and characteristics of the model are horizontally distributed as a system of representative points and runoff formation complexes in space, and vertically, deep into the soil column and layers of underground runoff. Most parameters have strong physical meaning and are assessed a priori. The set of parameters describing one landscape can be used both for small and large basins without change of values.

The parameters of the model can be divided into five groups according to landscape components: soil column (unsaturated zone), vegetation cover, slope surface, underground runoff and climate parameters.

 

  • Soil (unsaturated zone) for different soil depths: density; porosity; maximum water holding capacity; infiltration coefficient; specific heat capacity and conductivity; the index of ice content influence at infiltration; the contribution ratio to evaporation; hydraulic parameter of soil runoff elements.
  • Vegetation cover: four phenological dates; maximum and minimum values of seasonal shadow fraction by vegetation cover; interception water capacities; landscape albedos; the coefficients of potential evaporation; and the coefficient of evaporation from the interception storage during the maximum development of vegetation cover.
  • Slope surface: maximum and minimum values of the snow redistribution coefficient; spatial variation coefficient of SWE in snow cover; spatial variation of infiltration capacity of upper soil layer; maximum ponding fraction; maximum surface depression storage; and hydraulic parameter of surface runoff elements. The parameters describing snow characteristics are assessed against snow survey data.
  • Underground system of runoff elements: the hydraulic parameter and redistribution values. The hydraulic parameter is usually assumed to be constant; the values of redistribution of water volume among modelling groundwater layers are assigned on the basis of observed hydrograph analysis within the concept of runoff elements. For runoff hydrographs of similar type these values are closely related.
  • Climate parameters, if not obtainable, are estimated using the forcing meteorological data.