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See detailDifferent methods for spatial interpolation of rainfall data for operational hydrology and hydrological modeling at watershed scale: a review
Ly, Sarann ULg; Charles, Catherine ULg; Degré, Aurore ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(2), 392-406

Watershed management and hydrological modeling require data related to the very important matter of precipitation, often measured using raingages or weather stations. Hydrological models often require a ... [more ▼]

Watershed management and hydrological modeling require data related to the very important matter of precipitation, often measured using raingages or weather stations. Hydrological models often require a preliminary spatial interpolation as part of the modeling process. The success of spatial interpolation varies according to the type of model chosen, its mode of geographical management and the resolution used. The quality of a result is determined by the quality of the continuous spatial rainfall which ensues from the interpolation method used. The objective of this article is to review the existing methods for interpolation of rainfall data that are usually required in hydrological modeling. We review the basis for the application of certain common methods and geostatistical approaches used in interpolation of rainfall. Previous studies have highlighted the need for new research to investigate ways of improving the quality of rainfall data and ultimately, the quality of hydrological modeling. [less ▲]

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See detailCatchment modelling and sensitivity analysis to spatial interpolation methods of daily rainfall
Ly, Sarann ULg

Doctoral thesis (2012)

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to ... [more ▼]

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to continuous surfaces. The objective of this dissertation is to confront the performances of the several spatial interpolation methods, in particular the geostatistics for daily rainfall data in the nested catchments to realize a sensitivity analysis on discharges modelled at the outlets to the daily rainfall input in the modelling. The previous studies in the literature emphasized a requirement of novel investigation on the essential means to recover the rainfall data and eventually, the quality of the hydrological modelling. This study leaned on 30-year daily rainfall data of 70 raingages in the hilly landscape of the Ourthe and Ambleve catchments in Belgium (2908 km²). Two common deterministic methods are employed here. The Thiessen Polygon (THI) assigns the value from the nearest observation to a certain grid cell. The Inverse Distance Weighting (IDW) is an advanced nearest neighbour approach that allows including more observations than only the nearest points. The value at a certain grid cell is obtained from a linear combination of the surrounding locations. In the geostatistical algorithms, the spatial variation may be better described by a stochastic function. Four versions of kriging are used. The Ordinary Kriging (ORK) is the basic form of Kriging that the prediction is also a linear combination of the measured values. But the spatial correlation between the data, as described by the variogram, determines the weights, assuming that the mean is constant but unknown. The Universal Kriging (UNK) is based on the hypothesis that this mean is a polynomial function of spatial coordinates. So, this type of kriging is not stationary with regard to the mean. The Kriging with External Drift (KED) supposes that the mean of the interest variable depends on auxiliary variables; the theory of this kriging is in fact the same as the theory of UNK, which also contains a non-constant mean. The drift is defined externally through some auxiliary variables. The Ordinary Cokriging (OCK) suggests estimating the variable of interest by weighted linear combination of its observations and the observations of the auxiliary variables. This technique requires the study of the spatial dependence between variables besides the study of the simple spatial dependences. All types of kriging use a variogram model to characterise spatial correlation. A variogram describes in terms of variances how spatial variability changes as a function of distance. Seven semi-variogram models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) were fitted to daily sample semi-variogram on a daily basis. These seven variogram models were also adopted to avoid negative interpolated rainfall. The elevation, extracted from a digital elevation model, was incorporated into multivariate geostatistics. Seven validation raingages and cross validation were used to compare the interpolation performance of these algorithms applied to different densities of raingages. The areal rainfalls are calculated for the catchment area and used for analysis of extreme rainfall. The effects of the interpolation methods on the extreme rainfall are analysed. The interpolated rainfalls are also used as rainfall input of the physically-based and distributed EPIC-GRID model. The long series of model results are analysed by comparison with the observed discharges at the different outlets of the catchments. Then, the extreme discharges at the outlets are computed. All of these investigations always take into account of the raingage density and the raingage position for very sparse raingage cases. The main results show that among the methods based on the only rainfall data, the geostatistics and IDW are the best ones. The performances change according to the density of the raingages. For the extreme rainfall and long term modelling results, no big difference is found for a high density of raingage but large difference are found for the case of the scattered raingage. For the latter case, UNK and KED are very sensitive to the position of the raingages. IDW, ORK and OCK are found to be the best performance. However for the extreme flow, KED and OCK is the best whereas IDW is not better for the high density of the raingages. For the case of the scattered raingages, the difference in extreme discharge between the interpolation methods is very large and larger than shown in the extreme rainfall and the long term modelling results. IDW, ORK and OCK always perform better. UNK and KED still are sensitive to the positions of raingages. The index of position is used to describe the form of polygon defined by the four raingages. This index is defined as the relation between the polygon perimeter and a circle perimeter having an area equivalent to that of the polygon. The best raingage position for all interpolation methods used in this research should be arround the catchment area, its index should be close to one. [less ▲]

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See detailEffect of raingage density, position and interpolation on rainfall-discharge modelling
Ly, Sarann ULg; Sohier, Catherine ULg; Charles, Catherine ULg et al

in Geophysical Research Abstracts (2012), 14(EGU2012), 2592

Precipitation traditionally observed using raingages or weather stations, is one of the main parameters that has direct impact on runoff production. This pPrecipitation data requires a preliminary spatial ... [more ▼]

Precipitation traditionally observed using raingages or weather stations, is one of the main parameters that has direct impact on runoff production. This pPrecipitation data requires a preliminary spatial interpolation prior to hydrological modeling. The accuracy of modelling result is determined bydepends on the accuracy of the interpolated spatial rainfall which differs according to different interpolation methods. The accuracy of the interpolated spatial rainfall is usually determined by cross-validation method. The objective of this study is to assess the different interpolation methods of daily rainfall at the watershed scale through hydrological modelling and to explore the best methods that provides a good long term simulation. Four versions of geostatistics: Ordinary Kriging (ORK), Universal Kriging (UNK), Kriging with External Dridft (KED) and Ordinary Cokriging (OCK) and two types of deterministic methods: Thiessen polygon (THI) and Inverse Distance Weighting (IDW) are used to produce 30-year daily rainfall inputs for a distributed physically-based hydrological model (EPIC-GRID). This work is conducted in the Ourthe and Ambleve nested catchments, located in the Ardennes hilly landscape in the Walloon region, Belgium. The total catchment area is 2908 km², lies between 67 and 693 m in elevation. The multivariate geostatistics (KED and OCK) are also used by incorporating elevation as external data to improve the rainfall prediction. This work also aims at analysing the effect of different raingage densities and position used for interpolation, on the stream flow modelled to get insight in terms of the capability and limitation of the geostatistical methods. The number of raingage varies from 70, 60, 50, 40, 30, 20, 8 to 4 stations located in and surrounding the catchment area. In the latter case, we try to use different positions: around the catchment and only a part of the catchment. The result shows that the simple method like THI fails to capture the rainfall and to produce good flow simulation when using 4 raingages. The KED and UNK are comparable to other methods for a raingage case that in which stations are located around the catchment area, especially in the high elevation catchment but the worst methods for other raingage position cases where the rainfall stations are located only at a part and mostly outside of the catchment area. However, three methods (IDW, ORK and OCK) can overcome this problem since they are more robust and can provide good performance of simulation in all raingage densities. When using 70, 60, 50, 40, 30, 20, 8 raingages in the catchment area (2908 km²), no substantial differences in model performance are observed. [less ▲]

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See detailApplication of the TANK Model to a Tropical Monsoon Catchment in the Tonle Sap Lake Region of Cambodia
Someth, Paradis; Chanthy, Sochiva; Kubo, Naritaka et al

in Proceeding of The 4th AUN/Seed-Net Regional Conference on Geo-Disaster Mitigation in ASEAN (2011, October 25)

This paper presents an application of TANK Model to a sub-catchment of the Tonle Sap Lake of Cambodia. The TANK Model was developed in Japan and was reported as being successfully applied to many river ... [more ▼]

This paper presents an application of TANK Model to a sub-catchment of the Tonle Sap Lake of Cambodia. The TANK Model was developed in Japan and was reported as being successfully applied to many river basins in Africa, Asia, Europe and the United States. The objective of this study is to investigate the performance of the TANK Model in tropical monsoon climate condition. The studied area is a sub-catchment of the Tonle Sap Lake. Two automatic hydrological stations and four automatic telemetry meteorological stations were installed in the sub-catchment. Rating curves at the two hydrological stations was established. The performances of the rating curves and the TANK model were assessed by four standard statistical evaluations. The model was calibrated by discharge derived from the rating curves. The runoff pattern from the TANK Model correlated closely with rainfall pattern. The model could estimate runoff for the wet season, except for some peak flows generated from delayed runoffs. However, the model tended to overestimate dry season flow and react faster to rainfall events in the dry season. [less ▲]

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See detailGeostatistical interpolation of daily rainfall at catchment scale: the use of several variogram models in the Ourthe and Ambleve catchments, Belgium
Ly, Sarann ULg; Charles, Catherine ULg; Degre, Aurore ULg

in Hydrology & Earth System Sciences (2011), 15(7), 2259-2274

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to ... [more ▼]

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to continuous surfaces. The first step in kriging computation is the semi-variogram modelling which usually used only one variogram model for all-moment data. The objective of this paper was to develop different algorithms of spatial interpolation for daily rainfall on 1 km2 regular grids in the catchment area and to compare the results of geostatistical and deterministic approaches. This study leaned on 30-yr daily rainfall data of 70 raingages in the hilly landscape of the Ourthe and Ambleve catchments in Belgium (2908 km2). This area lies between 35 and 693 m in elevation and consists of river networks, which are tributaries of the Meuse River. For geostatistical algorithms, seven semi-variogram models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) were fitted to daily sample semi-variogram on a daily basis. These seven variogram models were also adopted to avoid negative interpolated rainfall. The elevation, extracted from a digital elevation model, was incorporated into multivariate geostatistics. Seven validation raingages and cross validation were used to compare the interpolation performance of these algorithms applied to different densities of raingages. We found that between the seven variogram models used, the Gaussian model was the most frequently best fit. Using seven variogram models can avoid negative daily rainfall in ordinary kriging. The negative estimates of kriging were observed for convective more than stratiform rain. The performance of the different methods varied slightly according to the density of raingages, particularly between 8 and 70 raingages but it was much different for interpolation using 4 raingages. Spatial interpolation with the geostatistical and Inverse Distance Weighting (IDW) algorithms outperformed considerably the interpolation with the Thiessen polygon, commonly used in various hydrological models. Integrating elevation into Kriging with an External Drift (KED) and Ordinary Cokriging (OCK) did not improve the interpolation accuracy for daily rainfall. Ordinary Kriging (ORK) and IDW were considered to be the best methods, as they provided smallest RMSE value for nearly all cases. Care should be taken in applying UNK and KED when interpolating daily rainfall with very few neighbourhood sample points. These recommendations complement the results reported in the literature. ORK, UNK and KED using only spherical model offered a slightly better result whereas OCK using seven variogram models achieved better result. [less ▲]

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See detailEffects of different spatial interpolators on the estimate of extreme precipitations
Ly, Sarann ULg; Beckers, Eléonore ULg; Charles, Catherine ULg et al

in Geophysical Research Abstracts (2011), 13

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The ... [more ▼]

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The problem involves choosing the interpolation method that we should use to estimate the extreme event. This work aimed at analyzing the effects of different interpolation methods on the estimate of extreme events of daily areal precipitations at catchment scale. The extreme rainfalls were estimated using areal daily rainfall interpolated by several interpolation methods (Thiessen polygon, Inverse Distance Weighting, Ordinary Kriging, Universal Kriging, Kriging with an External Drift and Ordinary Cokriging). We used thirty-years-long daily time series and different density of rain gages (from 4 to 70 rain gages). Our study is located in the Ourthe and Ambleve catchment area (2908 km²) in the southern part of Belgium). Spatial interpolation with the geostatistical and Inverse Distance Weighting algorithms outperformed considerably interpolation with the Thiessen polygon. Kriging with an External Drift and Ordinary Cokriging presented the highest Root Mean Square Error between the geostatistical and Inverse Distance Weighting methods. Ordinary Kriging and Inverse Distance Weighting were considered to be the best methods, as they provided smallest Root Mean Square Error for nearly all cases. However, it’s not really the case of extreme estimates for particular return period. The extreme daily rainfall, corresponding to return periods of 25, 50 and 100 years, were computed by fitting of a statistical model to the series of maximum annual precipitation. These estimates were conducted using HYFRAN which allows us to fit 16 different statistical models, in 2 or 3 parameters. The most known are the models of Gumbel, Gamma, Weibull, exponential, Pareto, lognormale, Pearson III and GEV. Our results showed that the behaviour of extreme daily areal rainfall in this area was best described via the Gumbel and lognormal distributions. Using 70 rain gages, little differences in extreme rainfall were observed between the interpolation methods. The estimates from these methods were in the area of 95% confidence intervals of the estimates using the Thiessen polygon. However, when the number of rain gages diminishes, the Universal Kriging and Kriging with External drift methods produced extreme estimates outside the area of 95% confidence intervals of the estimates using the Thiessen polygon with all available stations. The analysis described here provides a means to choose the interpolation method in view to calculate extreme events. It shows to engineers or hydrologists the need for a particular care when working in the regions of sparse data. [less ▲]

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See detailComparison of agricultural soils' structure depending on tillage system using X-ray microtomography
Beckers, Eléonore ULg; Ly, Sarann ULg; Léonard, Angélique ULg et al

in Geophysical Research Abstracts (2010, May), 12

This study aims at characterizing agricultural soils’ structure depending on the tillage system: conventional tillage or conservational tillage. Tillage reduction is an increasing practice, but the micro ... [more ▼]

This study aims at characterizing agricultural soils’ structure depending on the tillage system: conventional tillage or conservational tillage. Tillage reduction is an increasing practice, but the micro-structural effects on soils and on their hydrodynamic parameters are still not well described. Recent research shows non-converging results. Our point is to highlight fundamental differences in structure through characterization of soils porosity’s parameters using X-ray microtomography measurements coupled to image analysis. This attempt is in line with a more integrated experiment of which the aim is to quantify the effects of tillage intensity on lateral flow production, and finally on global water balance. Parameters’ measurements consist in a combined approach, based on two different space-time scales of exploration: fundamental scale, with soil sampling campaign for microtomography analysis, and field scale, with continuous flow measurements (plots’ dimensions: 18*28 m). For their part, parameters for water balance determination (precipitation, evapotranspiration…) are monitored on the field. All of these measurements have the main objective of hydrological modeling enhancement by taking into account a better lateral flow description. Discussion in this paper will focus on the first results obtained by X-ray microtomography measurements. Our experiment takes place in Gentinnes (Walloon Brabant, Belgium), on a field organized in a split-plot scheme. Since 2004, plots have been cultivated in conventional tillage or in reduced tillage. The latter consists in sowing after stubble ploughing of about 10cm. The crop rotation is sugar beet followed by winter wheat. The soil is mainly composed of silt loam. Soils samples, with a 3 cm diameter and a 5 cm height, were removed from the upper layer (Ap horizon) for both management practices. Samples are scanned by X-ray microtomography using a Skyscan-1172 high-resolution desk-top micro-CT system (Skyscan, Kontich, Belgium). The cone beam source operated at 100 kV, using an aluminium filter. The detector configuration, i.e. 1048×2000 pixels 16-bit X-ray camera, and the distance source-object-camera were adjusted to produce images with a pixel size of 17 µm. This resolution allows us to visualize both meso- and macro- porosity. In this study, half the samples were placed under a 15000 kPa pressure (corresponding pressure for the wilting point) in Richards’ apparatus in order to empty the meso- and macro-porosity. To determine a priori the class of porosity for the samples, relations between water retention and pressure head can be plotted using this apparatus. Scanning results consist in 2D images. The 2D images are recombined to form 3D structure. Then the pore network can be analyzed through useful factors like size distribution, shape, connectivity, orientation, tortuosity etc. [less ▲]

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See detailSpatial interpolation of daily rainfall in Ourthe and Ambleve Basins, Belgium
Ly, Sarann ULg; Sohier, Catherine ULg; Charles, Catherine ULg et al

in Geophysical Research Abstracts (2010, May)

Spatial interpolation of precipitation data is of great importance for hydrological modelling. The methods of geostatistics (krigings) become more popular to make spatial interpolation from point ... [more ▼]

Spatial interpolation of precipitation data is of great importance for hydrological modelling. The methods of geostatistics (krigings) become more popular to make spatial interpolation from point measurement to distributed hydrological models. However, most of existing geostatistic algorithms are available only for single-moment data. The first step of Kriging computation is the semi-variogramme modelling which usually uses only one variogramme model for all-day data. The objective of this paper is to review the implementation of an algorithm of spatial interpolation methods for daily rainfall and to compare the results of geostatistic and deterministic approaches. In this study, we will use daily rainfall data from 70 rain gauges in the hilly landscape of Ourthe and Ambleve Basins in Belgium (2751 km2). This area lies between 35 and 690 m in elevation and consists of river networks which are the tributaries of the Meuse River. The proposed algorithm will use the method of Cressie’s Approximate Weighted Least Squares to fit among sevens semi-variogramme models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) to daily sample semi-variogrammes. These seven models are computed on a daily basis. Firstly, one model is chosen by considering the minimum of least squares coefficient. Secondly, if the chosen model gives negative interpolated values, other models will be chosen again until the result become positive. Cross validation will be used to compare the interpolation performance of geostatistic to deterministic methods usually known as Thiessen polygon and Inverse DistanceWeighting (IDW). [less ▲]

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See detailRing dike system to harness floodwater from the Mekong River for paddy rice cultivation in the Tonle Sap Lake floodplain in Cambodia
Someth, Paradis; Kubo, Narita; Tanji, Hajime et al

in Agricultural Water Management (2009), 96

Located in the floodplain of the Mekong River and the Tonle Sap River, Batheay irrigation system and its reservoir directly receive floodwater from the Mekong. The Batheay reservoir formedby a ring dike ... [more ▼]

Located in the floodplain of the Mekong River and the Tonle Sap River, Batheay irrigation system and its reservoir directly receive floodwater from the Mekong. The Batheay reservoir formedby a ring dike functions as botha reservoir anda paddy field. In thewet season, the ring dike prevents floodwater fromentering the reservoir and rainy season rice is growninside the dike. After harvesting, the gateson the ring dike are openedto receive floodwater. The water is stored inside the dike for cultivating dry season rice outside the dike. In this paper, the irrigation system is studied as a model site for future development of the floodplain of the Tonle Sap Lake of Cambodia. Specifically, this paper is concerned with the study of water balance and analysis of the hydrologic components of the Batheay irrigation system, and the effectiveness of the ring dike system. The study found that floodwater of the Mekong River contributed about 74% to the total inflow to the Batheay reservoir. Contributions to the total water supply of reservoir water, floodwater remaining in the fields, and precipitation were 73, 12, and 15%, respectively. The efficiency of the systemwas found to be 92%. The dike system is expected to be a paradigm for the floodplain of the Tonle Sap Lake. [less ▲]

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See detailMAIN EXISTING IRRIGATION SYSTEMS IN THE SUB-BASINS OF THE TONLE SAP LAKE OF CAMBODIA
Ly, Sarann ULg; Someth, Paradis

Poster (2008, September 11)

The Tonle Sap Lake and its complex tributaries are the main water body and water courses of Cambodia. The catchment area of the lake is generally divided into twelve major sub-basins. The tributaries of ... [more ▼]

The Tonle Sap Lake and its complex tributaries are the main water body and water courses of Cambodia. The catchment area of the lake is generally divided into twelve major sub-basins. The tributaries of the lake have great potential of water resources for agricultural and industrial development. The river networks and existing irrigation projects are not well surveyed. A survey trip was conducted around the lake. The aim of this trip is to understand the river networks and identify main existing irrigation systems in the sub-basins of the Tonle Sap Lake. In this poster, we are mainly focused on the existing irrigation schemes. The schemes are classified into five categories. (1) “Surface runoff collector”: it is formed by a small dike to collect surface runoff from upstream part. The water collected is used as a supplementary water source for rainy season cultivation and for irrigating a small area of dry season cultivation. (2) “Dam reservoir”: a dam is put in place on a river to store the river runoff during the rainy season and the water stored is supplied to a command area in the dry season. (3) “Indirect diversion”: it is characterized by a diversion structure and a storage reservoir. Water is diverted and stored in the reservoir during the rainy season and used for dry season cultivation. (4) “Direct diversion”: characteristic of this type is similar to that of the indirect diversion, except the river water is diverted directly to irrigated area without storing in a reservoir. (5) “Flood storage”: it is generally developed in the floodplain of the Tonle Sap Lake. A ring dike prevents floodwater from entering the reservoir and rainy season rice is grown inside the dike. After harvesting, the gates on the ring dike are opened to receive floodwater. The water is stored inside the dike for cultivating dry season rice outside the dike. This study found that there are only small-scale irrigation schemes developed around/in the Tonle Sap Lake. The water resources of this lake have not been effectively used. [less ▲]

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See detailWATER QUALITY AND POLLUTION CONTROL IN PHNOM PENH, CAMBODIA
men, nareth; Ly, Sarann ULg; ann, vannak et al

Conference (2008)

The urban infrastructure, particularly water supply and drainage systems, have deteriorated severely in the past two decades in Phnom Penh, the capital city and the economic center of Cambodia. Water ... [more ▼]

The urban infrastructure, particularly water supply and drainage systems, have deteriorated severely in the past two decades in Phnom Penh, the capital city and the economic center of Cambodia. Water pollution caused by untreated wastewater is one of the serious problems that confront most developing countries (Kwai et al.1991). In Phnom Penh City, all kinds of wastewater are discharged to rivers, lakes and wetlands throughout the city without proper treatment causing serious surface water pollution. Water testing is an essential factor to control water pollution. However, water quality data and water quality testing systems are still poorly developed in Cambodia due to lack of facilities and technical expertise. Therefore, there is no information available on sewage water quality in Phnom Penh City. That’s why the work is aimed at collating basic information about the situation of water supply, waste water system and solid waste. The present information will provide the basis for targeting further field research. This is included the overview of sources and activities that may lead to pollution, with an appreciation of type of water pollutants involved, their magnitude and movement. Types of waste and effluent disposal including sanitation, liquid and solid waste management systems are described. After reviewing all the available, we found that the distribution of water has been well organized by the Phnom Penh Water Supply Authority while the managements of the wastewater, storm water and solid waste are poor due to the rapid urbanisation and industrialisation. [less ▲]

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See detailModel of Irrigation Development for Floodplain of the Tonle Sap Great Lake
someth, Paradis; Kubo, n; Ly, Sarann ULg et al

Poster (2008)

Rice is a staple crop in Cambodia. To meet the large requirement of rice consumption due to rapid increased population and to boost the economy, the rice production in this country needs to be enhanced ... [more ▼]

Rice is a staple crop in Cambodia. To meet the large requirement of rice consumption due to rapid increased population and to boost the economy, the rice production in this country needs to be enhanced. The Tonle Sap Great Lake of Cambodia has huge floodplain suitable for large amount for rice production and potential water resources for rice-based farming system. Due to large variation of water level of the lake, some areas around the lake are flooded in wet season and shortage of water in dry season. Studies to exploit the flood and the water rsources of the lake and its tributaries have not been well conducted yet. The West Baray and Batheay irrigation systems are located in the floodplain of the Tonle Sap Great Lake and the Mekong River. In this research, the irrigation systems are studied as model sites for future development of the floodplain of the Tonle Sap Great Lake. [less ▲]

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See detailModels of irrigation system for Pursat basin planning
Ly, Sarann ULg; Someth, Paradis; Men, Nareth

Poster (2007, May 14)

The Mekong River and the Tonle Sap Great Lake in Cambodia have vast floodplain suitable for rice-based farming system. The Tonle Sap Basin, defined as the catchments of the Tonle Sap River at its ... [more ▼]

The Mekong River and the Tonle Sap Great Lake in Cambodia have vast floodplain suitable for rice-based farming system. The Tonle Sap Basin, defined as the catchments of the Tonle Sap River at its confluence with the Mekong River and other 11 main tributaries draining higher ground on all sides of the basin enclosing 44% of Cambodia’s land area. The Pursat River is one of tributaries of the Tonle Sap Great Lake. It originates at Cardamom Mountains and has very good potential for agricultural development. In this paper, we aim at applying three models of irrigation system for basin planning: Chinit (Dam-Reservoir Irrigation), West Baray (Reservoir Irrigation) and Batheay (Shallow Reservoir Irrigation) to Pursat Basin (one of sub-basin of the Tonle Sap Great Lake). Chinit Dam-Reservoir stores water supplied by one of tributaries of Tonle Sap Great Lake, the Chinit River, located in Kampong Thom Province. Spillway is built to pass up inundation and to release water to downstream part. The rest of water in the Dam-Reservoir is distributed to the paddy field by main canal, secondary canals and tertiary canals. This system can be put at the upstream part of the Pursat River, mountainous area. The West Baray Irrigation system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system situated in Siem Reap province. The reservoir is supplied by a tributary of the Tonle Sap Great Lake, the Siem Reap River, in rainy season. The water is distributed to irrigation area in dry season. A small dike system was constructed in the Tonle Sap floodplain for retarding and storing floodwater. The stored floodwater is used as an additional water source for dry season cultivation. This system can be placed at the central plain of the Pursat Basin. Batheay reservoir directly receives floodwater from the Mekong River. It functions as both a reservoir and a paddy field. In wet season, dike around the Batheay reservoir prevents floodwater from entering the reservoir. Rainy season rice is grown inside the reservoir. After harvesting, gates around the reservoir are opened to receive floodwater. The water is stored for cultivating dry season rice outside the reservoir. This system can be put at the downstream part of the Pursat River, floodplain area of Tonle Sap River. [less ▲]

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See detailPADDY IRRIGATION SYSTEM USING SHALLOW RESERVOIR IN THE MEKONG RIVER FLOODPLAIN
Ly, Sarann ULg; Someth, Paradis; Men, Nareth

in The Proceeding of the 5th International Symposium on Earth Resources and Geological Engineering Education (2007)

The Tonle Sap Great Lake and the Mekong River in Cambodia have huge floodplain suitable for rice-based farming system and potential water resources for farming. Studies to exploit the flood and the water ... [more ▼]

The Tonle Sap Great Lake and the Mekong River in Cambodia have huge floodplain suitable for rice-based farming system and potential water resources for farming. Studies to exploit the flood and the water resources of the lake and the river have not been well conducted yet. Batheay irrigation system is located in the floodplain of the Tonle Sap River and the Mekong River. In this research, the irrigation system is studied as a model site for future development of the floodplain of the Tonle Sap Great Lake and the Mekong River. Batheay reservoir directly receives floodwater from the Mekong. It functions as both a reservoir and a paddy field. In wet season, dike around the Batheay reservoir prevents floodwater from entering the reservoir. Rainy season rice is grown inside the reservoir. After harvesting, gates around the reservoir are opened to receive floodwater. The water is stored for cultivating dry season rice outside the reservoir. In this work, we attempt to study water management of the Batheay irrigation system by analyzing water use pattern in the irrigation system and uncover effectiveness of the system. A development scenario for the floodplain of the Mekong River is then proposed. [less ▲]

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See detailPOTENTIAL OF WATER RESOURCES OF PURSAT BASIN FOR IRRIGATION DEVELOPMENT
Ly, Sarann ULg; Someth, Paradis; Seng, Bunrith et al

in Tanji, Hajime (Ed.) Proceedings of the Second International Symposium on Sustainable Development in the Mekong River Basin (2006, September 18)

Pursat River, one of the tributaries, flows into the Great Lake Tonle Sap, located in Pursat province, 187 km from Phnom Penh. Pursat River originates in Kbal Kmaoch Mountain at an elevation of 1,425m ... [more ▼]

Pursat River, one of the tributaries, flows into the Great Lake Tonle Sap, located in Pursat province, 187 km from Phnom Penh. Pursat River originates in Kbal Kmaoch Mountain at an elevation of 1,425m. The main stream joins with Prey Khlong River and Arai River which originate in Orall Mountain at the elevation of 1,813m, the highest mountain in Cambodia. Large of paddy field in the province is irrigated by the river. The lack of year round management of irrigation system along the river is a serious constraint to social and economic development, and poverty reduction in the province. The objective of the research is to discover the appropriate way to develop the irrigation system along the river. The study attempts to uncover the historical development of the river and water use along the river. The research also reveals the appropriate way to put the right system to the right place. The analysis will review the estimation of river flow and total annual flow, an amount of water to be withdrawn from the river, which will be simulated based on meteorological and hydrologic data, and field investigation. [less ▲]

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Peer Reviewed
See detailDEVELOPMENT OF SHALLOW RESERVOIR IRRIGATION BY USING FLOODWATER FOR PADDY RICE CULTIVATION
Someth, Paradis; Kubo, N.; Ly, Sarann ULg et al

in Tanji, Hajime (Ed.) Proceedings of the Second International Symposium on Sustainable Development in the Mekong River Basin (2006, September 18)

The Tonle Sap Great Lake and the Mekong River in Cambodia have huge floodplain suitable for rice-based farming system and potential water resources for farming. Studies to exploit the flood and the water ... [more ▼]

The Tonle Sap Great Lake and the Mekong River in Cambodia have huge floodplain suitable for rice-based farming system and potential water resources for farming. Studies to exploit the flood and the water resources of the lake and the river have not been well conducted yet. Batheay irrigation system is located in the floodplain of the Tonle Sap River and the Mekong River. In this research, the irrigation system is studied as a model site for future development of the floodplain of the Tonle Sap Great Lake and the Mekong River. Batheay reservoir directly receives floodwater from the Mekong. It functions as both a reservoir and a paddy field. In wet season, dike around the Batheay reservoir prevents floodwater from entering the reservoir. Rainy season rice is grown inside the reservoir. After harvesting, gates around the reservoir are opened to receive floodwater. The water is stored for cultivating dry season rice outside the reservoir. In this work, we attempt to study water management of the Batheay irrigation system by analyzing water use pattern in the irrigation system and uncover effectiveness of the system. This study plays a vital role in the study of the Tonle Sap Great Lake system in our future research. [less ▲]

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Full Text
See detailExactitude et précision de la mesure de superficie de parcelle de culture
Ly, Sarann ULg

Master of advanced studies dissertation (2005)

There are a number of important reasons for determining areas: natural resource valorisation and protection, environmental management or others works. But what is a data quality? Accuracy is characterised ... [more ▼]

There are a number of important reasons for determining areas: natural resource valorisation and protection, environmental management or others works. But what is a data quality? Accuracy is characterised by systematic errors and mistakes. When these errors are eliminated, the standard deviation qualifies the precision. It is characterized by the random errors that there is no absolute way to eliminate them and which obey the general law of normal distribution. Three formulas are selected according to instruments available to compute the culture parcel area: (1) Area by polar coordinates, (2) Area by rectangular coordinates and (2) formula of Sarron. When parameter measurements are subject to error, areas calculated from the parameters will also be in error. The statistical models associated to each formula are developed to evaluate the precision of area measurement and are checked by simulations. Three types of available instrument according to suitable methods: (1) Total Station, (2) GPS (RTK GPS and DGPS) and (3) Topofil and Compass (forest instruments). These instruments are used in the field to confirm the three variance computation formulas. For all instruments used, approximate and observed variances are equivalent. Two exceptions to this confirmation: the total station and DGPS in case of area determined by a small number of points. [less ▲]

Detailed reference viewed: 46 (7 ULg)