Procedia Engineering 154 ( 2016 ) 1010 – 1017

1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the organizing committee of HIC 2016doi: 10.1016/j.proeng.2016.07.590

ScienceDirectAvailable online at www.sciencedirect.com

12th International Conference on Hydroinformatics, HIC 2016

Applying deterministic distributed hydrological model for stream flow data reproduction. A case study of Cu De Catchment, Vietnam.

Vo Ngoc Duonga,b,*, Nguyen Quang Binhb, Le Xuan Cuongb, Qiang Maa, Philippe Gourbesvillea

aInnovative City lab URE 005, Polytech’Nice Sophia, Nice Sophia Antipolis University, France.

bFaculty of Water Resource Engineering, University of Science and Technology, the University of Da Nang, Vietnam.

Abstract

Deterministic distributed model has been confirmed as one of highest performance model for representing the hydrological regime. By the capacity of covering all hydrological components in a catchment, this model is expected to be an effective tool for restoring the stream flow data, especially at lack of data catchment. In this study, a deterministic hydrological model - MIKE SHE (DHI) - is applied for reproducing the daily flow data in 20 years of Cu De river catchment, Viet Nam. The model is constructed over 425.2 Km2 with most of catchment's hydrological components. These components are set up in principle based on the characteristics of neighbouring catchment, Vu Gia - Thu Bon. © 2016 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of HIC 2016.

Keywords: Deterministic distributed model; Cu De river; catchment management.

1. Introduction

Water is indispensible for life and plays an important role for the human society (Gleick, 1993; Watkins, 2006).

* Corresponding author.

E-mail address: vongo0@aquacloud.net

© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of the organizing committee of HIC 2016

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However, its distribution is not equal due to time, space. It leads to many natural disasters and influences natively to social economic development. Furthermore, in recent years, under the impact of climate change, the consequences of natural disaster related to water are more frequent and serious (Vázquez et al., 2002). With above reasons, there is a need to study the river run off regime and catchment hydrological process, which are hoped to provide an overall knowledge for mitigating the impact of these disasters to human society.

Modelling is considered as the good way for studying the happening in catchment’s hydrological regime. Nowadays, with the development of mathematics and computer science, the simulation of hydrological cycle for catchment becomes easier and more accurate (Blöschl & Sivapalan, 1995). Nevertheless, this work has been facing lots of difficulties such as available data, computational capacity. These problems might be more complicated towards developing countries where database has been not built completely. Towards these catchments, flow reproduction using deterministic distributed model is seen as the best ways for overcoming the data limitation.

This paper will be presented an experience in using deterministic distributed model to reproduce the river flow in a lack of data catchment. The study is realized in Cu De catchment, a small catchment in central Vietnam. Based on recent result of neighbouring catchment, Vu Gia Thu Bon catchment, the flow of Cu De river is reproduced in 20 years.

2. Study area

The Cu De is second large river catchment of Da Nang city and is one of main supplied water resource of Da Nang city. It covers an area up to 425.2 km2 (Figure 1). This is located at the edge of the largest rainfall region Quang Nam - Da Nang. The catchment’s aaverage annual rainfall is quite high, approximately 1800 mm. However, there is a difference in the season, 65% - 80% of annual rainfall concentrated in the period August - December. Moreover, this

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area is under attack every year from 2 - 4 storm bringing heavy rains and whirlwinds (RETA 6470, 2011; TO, 2005). This severe weather pattern makes the natural disaster occurs frequently and seriously.

Figure 1. Cu De catchment

3. Methodology

The proposed principle for Cu De river’s flow reproduction is based on the similar of its catchment characteristic with another one and on the deterministic distributed model ( Figure 2). The selected model here is Vu Gia Thu Bon,

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a large catchment located close to Cu De. The Vu Gia Thu Bon has been studied seriously in previous times. Especially in recent study, Vo & Gourbesville, (2016) provides basically an overview about Vu Gia Thu Bon catchment’s hydrological process in 20 years. The study of these authors determined principal parameters of Vu Gia Thu Bon catchment. With assuming that the characteristic of these two catchments is almost the same and using deterministic distributed model, the flow of Cu De is able to replicated relied on Vu Gia Thu Bon catchment’s parameter.

Figure 2. Proposed methodology for steam flow reproduction.

3.1. Deterministic distributed hydrological model - MIKE SHE

The MIKE SHE model has been developed and extended by DHI Water & Environment since the last decades of the 20st century (DHI, 2012). MIKE SHE covers the major processes in hydrologic cycle and includes process models for evapo-transpiration, overland flow, unsaturated flow, groundwater flow, channel flow, and their interactions (Figure 3).

Figure 3. Schematic of MIKE SHE model (DHI, 2012)

Each of these processes can be represented at different levels of spatial distribution and complexity, according to

the goals of modelling study, the availability of field data and the modeler’s choices(Butt et al., 2004). Hence, it helps to increase the quality of hydrological simulation. Due to its performance, MIKE SHE has been used in a broad range of applications. It is being used operationally in many countries around the world by organizations ranging from universities and research centers to consulting engineers companies (Refshaard, Storm, & Singh, 1995)

3.2. Model setup

The model is set up over an area of 425.2 Km2 and includes all of hydrological components in Cu De catchment with data as follows:

a. Topography: The topography data using in the model is taken from LUCCI project with the resolution is 15m x 15m.

b. Precipitation: The simulation uses the rainfall data that are re-distributed spatially based on daily rainfall data from 15 rain gauge stations in Quang Nam - Da Nang with the Kriging method (Vo & Gourbesville, 2014) (Figure. 4a).

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Vo Ngoc Duong et al. / Procedia Engineering 00 (2016) 000–000 5

Figure 4. (a) Rainfall distribution and (b) River network at Cu De catchment.

c. Land use and Soil map: The land use and soil data are simplified from the data of project Land Use and Climate Change Interaction in Central Viet Nam (LUCCI), and project Impacts of Climate Change in Mi-Central Viet Nam (P1-08 VIE) (Figure 5a and 5b). d. Evapotranspiration: Data are inherited from the study of Vu et al,. (2008). e. Vegetation: The vegetation property in this simulation is gotten from DHI results (DHI, 2012). f. River and lakes: In order to simulate better the river flows, MIKE SHE model is coupled with a hydrodynamic

1D model - MIKE 11 model. The river network using in this study consists of twenty branches. The cross sections are from two sources: few of them at downstream are taken from the measurements, and the remaining ones are extracted from the DEM (Figure. 4b)

g. Overland flow: The main parameter to calculate this flow is Stickler roughness coefficient (M). This parameter is determined based on the land use map.

h. Unsaturated zone: The simple two-layer water balance method is applied for presenting the flow component in this zone. The physical property of each soil type is presented via the water content at saturation, water content at field capacity, water content at wilting point and saturated hydraulic conductivity.

i. Saturated zone: The groundwater is supplied by Central Viet Nam Division of Water Resources Planning and Investigation (http://www.ceviwrpi.gov.vn).

Figure 5. (a) Land use map and (b) Soil map at Cu De catchment.

(a) (b)

(a) (b)

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4. Validation and discussion

The model is constructed in period of 22 years, from 1990 to 2011 and represents all of hydrological component of Cu De catchment. The daily discharge is extracted at downstream overs 22 years; one first year is utilized for warming up the model. The result is demonstrated by discharge in Figure 6 and by flow module in Figure 7.

As mentioned above, there is a difficulty for studying the hydrological regime of Cu De catchment. Apparently, there is not thing for calibrating and validating the model. So in this study, reproduced flow is compared with flow module of past studies. The comparison is showed in the Table 1 in Figure 7, Figure 8 and Figure 9.

Figure 6. Hydrograph of discharge at Nam O bridge.

Comparing with the results from two last studies of CVIWR (2015), Nguyen (2005) and flow module of two stations (Nong Son, Thanh My) of neighboring catchment (Vu Gia Thu Bon) ( Vu et al., 2011), the reproduced flow is seemly reasonable and acceptable. The simulated flow module is mostly similar to the result of Nguyen (2005) in annual value, seasonal values as well.

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Figure 7. Annual flow module at Nam O.

However, the simulated flow module is less than result of project RCCWRDN (CVIWR, 2015) many time. This difference might be explained by considering the confidence of RCCWRDN’s result. The comparison reflects the inaccuracy in the result of RCCWRDN project. It is not possible when the flow of Cu De catchment is approximately equal with the flow of Thu Bon catchment and higher than the flow of Vu Gia Catchment. Even if these reference catchments are multiple 10 times in comparison with Cu De Catchment and they are located in a rainfall region having higher intensity than.

Figure 8. Flow module in flood season at Nam O;

Table 1. Flow module comparion.

Study catchment Reference catchment

RCCWRDN project

Nguyen (2005)

Simulation Vu Gia Thu Bon

Dry season 44.7 21 25.19 32,4 36,1

Flood season 229.9 120 112.45 162 233

Annual average 91 45.75 47.16 71.2 92.4

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Figure 9. Flow module in dry season at Nam O;

5. Conclusion

The aim of this study is to look for new way to reproduce the stream flow in lack of data catchment. By exploiting the strong point of deterministic distributed model and the result in neighboring catchment, the run off process in 21 years of Cu De river is replicated. The modelling result is quite similar to last studies in the region. This approach is expected to bring out a new solution in stream low reproduction. References

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