Regional Hydrlogy

Numerical Hydrology Model

A hydrologic system model is an approximation of the actual system; its inputs and outputs are measurable hydrologic variables conserning atmosphere, landsurface, and underground, and its structure is a set of equations linking the inputs and outputs. These models are usually calculated numerically by computer. With use of these hydrologic system models, we can understand whole temporal and spatial hydrological system, by forecasting, reproducing and estimating flood and drought.

Hydrological Modeling using data set by GIS/RS

GIS is a useful tool searching, treating, analyzing, and presenting geographical informations. Distributed Hydrologic Model which treats various data distributed geographically was developed in this study.
First, availability of this model was tested in Maehara river in Chiba prefecture. After that, infiltration facilities were set in this catchment and the effections of these infiltration facilities were varified by this model.
Fig.1:Application Catchment(1 by 100m)
(blue area:setting point)
Fig.2:Surface runoff map (Before setting facilities.)
(blue:high level water,yellow:river)
Fig.3:Surface runoff map (After setting facilities)
blue:high level water,yellow:river)

Infiltration facilities were setted as is shown in Fig.1. It is clear that the surface discharge as shown in Fig2. was decreased as shown in Fig.3 after infiltration facilities were setted.
We can gain the effection of infiltration facilities easily with this GIS-used model, because confirmations of the results of this model shown on maps is easily available like this. Though infiltration facilities were setted one for each 100m grid in this study, this model can be applied to planning of infiltration facilities, by proposing proper amount of infiltration facilities using maps of surface discharge predicted by the model.
SHINYA Tanimoto 1995 :Hydrological Modelling for Basin Management & Planning using GIS, Master thesis

Distributed Hydrologic Model using hillslope discretizetion based on catchment area function: Development and Applications

All figures will be normal size with click

The purpose of the study is to develop a new type of distributed hydrologic model which has the capabilities of:
1) distributed representation of spatial variations
2) physical descriptions of hydrologic processes
3) applicability to very large catchments
The main objectives include: development of model concept through the analysis of catchment geomorphological properties, model descripition, model validation, analysis of model sensitivity and applications.
Applications to medium size catchments were tested in three Japanese catchments which are located in humid temperate zone, namely Watarase river in Kanto region, Seki river in Hokuriku region and Naka river in Shikoku region.
The catchment areas range 700-1200 km2, and the meteorological gauges are densely located in these catchments.

Application to large catchment was tested in Chao Phraya river basin in Thailand which is located in tropic monsoon region. The simulation area is about 110000km2 (up to Nakhon Sawan).
The river discharge was compared with the simulation by grid-based distributed hydrologic model(GB model) gives better simulation results of river discharge.

Application to regional scale was tested in the lower Mekong river with limited available input data.
The simulation area in lower Mekong is about 400000km2 and the meteorological data are very limited. The hydrologic simulation has been carried out from 1989 to 1990 in hourly temporal resolution.
An acceptable river discharge result was obtained from the simulation.

(Simulation result in Naka river in Japan)

From the above applications, it is shown that the model can apply to different catchments of various sizes and climatic characteristics for both long term and flood simulations.

Yang, D. 1998 :Distributed Hydrologic Model using hillslope discretizetion based on catchment area function: Development and Applications, PhD Thesis

Process based soil erosion modelling at catchment scale.

The purpose of this study is to develope a process based soil erosion model which can simulate not only the total soil loss but also can give the variation in sediment loads with time (sediment graph), and also can be applied to relatively large catchments, as process based models are not yet applied at large catchment scales for the prediction of erosion.

The basic approach to develop a process based erosion model is the setting up of an existing hydrological model for a catchment under considerations, which can give inputs to the erosion model for overland flows and river flows. The slope based hydrological model has been selected for the proposed study as it contains one dimensional governing equations which considerably reduces the computational efforts required to run the model.
Then an erosion model with interril, rill, gully and channel components will be coupled with the hydrological model.

For the calibration and verification of the proposed process based soil erosion model, Nan river basin of Thailand has been selected. The total catchment area of the basin at Amphoe Muang Nan is 4609 km2, this section is situated at a latitude of 18 46’ 23” N and a longitude of 100 46’ 51” E.
At this gauge daily sediment concentration, daily water flow data is available. There are six rain gauges available within the catchment and one evaporation station out side the catchment, but within reasonable range.
It is also intended to apply this model to a sub-catchment of river Indus Pakistan for simulating the sediment loads which are generated due to hydrological processes over the area.

As the development of the erosion model is at the initial stage, so the results for the erosion part are not yet available for presentation. Although by now, the setting up process of the hydrological model has been completed and the results are presented on left.

normal size with click

HABIB Mughal, 2000 : Process based soil erosion modelling at catchment scale, Ph.D. Thesis