Sucharit Koontanakulvong

Surface water and groundwater dynamic interaction models as guiding tools for optimal conjunctive water use policies in the central plain of Thailand

Many irrigation projects in the central plain of Thailand are not capable of providing sufficient surface water for the cultivation of rice, which is the major cash crop for Thai farmers. To overcome this surface water deficiency, which has been exacerbated in recent years by climate change, groundwater is increasingly being used for irrigation. Thus, large sections of agriculture lands have been converted to conjunctive water use regions. While conjunctive water use may be a suitable option to overcome the temporary water shortages on a short-term basis, it may pose a particular threat to the overall water resources in the long term, if not properly managed. As a remedy, conjunctive water management policies ought to be adopted. Conjunctive water management is basically a tool to optimize productivity, equity, and environmental sustainability through simultaneous management of surface water and groundwater resources. As of now, such a comprehensive approach has not been yet employed in the upper Chao Phraya basin of Thailand, and the present study is one of the first of this kind. The study region is the Plaichumpol Irrigation Project (PIP) where conjunctive water use has become indispensable for meeting the increasing water requirements for farming. To get a first grip on the issue, water demand, supply and actual use in the study area were investigated for the purpose of providing possible guidelines for optimal water exploitation. A numerical groundwater model with a special module for simulating surface-groundwater interaction was applied in the PIP area to understand the impact of the farmer’s irrigation behavior on the dominant hydrological processes that determine the seasonal and multi-annual water availability in the irrigation area. A set-up of different agricultural water allocation schemes that depend on the local weather conditions and the regional management rules are examined by the numerical models. The results of the simulations provide adaptation guidelines for the proper management of the conjunctive water resources, namely, optimal water utilization. The numerical results for the surface groundwater in particular indicated that while the irrigation canals recharge water to the aquifer during both dry and wet season, small amounts of discharge from the aquifers to the canals occur only during the wet season. The analysis of the groundwater balance also showed that the present available groundwater potential is not fully exploited by the farmers, especially during the dry periods of surface water shortage. In contrast, the adoption of an optimal conjunctive management scheme would ensure extra water availability for additional annual rice crops in the region.

Lessons learned and information technology roles in Thailand floods 2011

July-November 2011, Central Plain of Thailand suffered from the serious flooding started from July in the northern area and the flood went downward to middle area and near Bangkok area in September and October. It was the first time that flood water reached the inner city of Bangkok and caused flash flood to many main industrial estates in the suburb of Bangkok. The damages of this flooding was estimated to be more than ten times of the previous major past flooding especially to the industrial sector and in the ranking number four of disaster damage in the world. During the flood event, the university had provided humanitarian assistances to the communities surrounding Bangkok in various forms including water information services. The flood reporting system consisted of two programs, i.e., flood reporting and flood planning. The system via social media helped informing the flood status from each individuals to share real time flood information through the system and also provided the basic information of ground level and water level from the nearby hydrological stations for flood preparation and rescue planning to the people. The information technology helped to convey such the information and massages in real time basis and help people to plan and prepare for flood fighting more efficient. In the Governments flood future plan, the flood information system was proposed to be an important element for flood warning and communication to communities and is included in both short and long term flood prevention measures. It is concluded that with the flood information system, people in the flood prone area can be better prepared for their fighting/rescue operations to save their lives and assets. Besides, the water information via telecommunication technology with good communication can better public flood operation of both public and personnel levels.

Statistical and Stochastical Approaches to Assess Reasonable Calibrated Parameters in a Complex Multi-Aquifer System

Effective assessment of reasonable calibrated aquifer parameters can be mainly divided into three categories; firstly, the conventional analysis of the misfit error between observed and calculated head, secondly, the calculation of sensitivity- and correlation coefficients and, finally, the pure stochastical approach applying well-known stochastical formulae (cf. Gelhar, 1993 ). We have applied these three approaches to the Bangkok Multi-Aquifer System. The latter consists of eight complex water bearing layers under Bangkok and neighboring provinces, namely, Bangkok Aquifer (BK - 50m.), Phra Pradang Aquifer (PD - 100m.), Nakhon Luang Aquifer (NL - 150m.), Nonthaburi Aquifer (NB - 200m.), Sam Khok Aquifer (SK- 300m.), Phaya Thai Aquifer (PT - 350m.), Thon Buri Aquifer (TB – 450m.) and Pak Nam Aquifer (PN - 550m.). Using first the conventional approach of trial and error, the geohydraulic parameters were estimated for this aquifer system by visual comparing observed and calculated heads. The regression graphs of observed head (x- axis) and calculated head (y-axis) showed all points located closely to the 45 degree-line, which indicates that calculated and observed heads conform closely to each other. Next, the estimated parameters were assessed by using the automated nonlinear regression program, UCODE (Hill, 1998). Relative composite scale sensitivity- and correlation coefficients are calculated. The results indicate that every estimated parameter has a composite scaled sensitivity higher than 0.01 and a correlation coefficient higher than 0.9, which shows that the corresponding geohydraulic parameters are well-determined and unique. This means that the observed heads are sufficient for a reliable calibration of the named parameters. In a third step, the full stochastical approach is used. Applying a random field generator (Chiang and Kinzelbach, 2001), 180 realizations of a logarithmic transmissivity field Y=lnT with a set of variances σY2 for each layer, namely, σY2 = 0.55, 0.77, 0.59, in layer 3, 4 and 5, respectively, and two sets of correlation length (λx, λy ) (with x and y corresponding to the EW and NS-direction, respectively) that represent 63% and 95% of the sill of the observed variograms, namely, λx = 9000, 6000, 5500 and λy = 12500, 23000, 7500 for the 63% -sill and and λx = 26000, 21500, 17500 and λy = 33000, 56000, 22500 for the 95%-sill which appears to characterize the possible stochastical range of the ln T –field in the multi-aquifer system. Using these Monte-Carlo simulations we investigate how σY2 contributes to the variance σH2 of the head and/or the residual head. It turns out that σY2 and σH2 estimated in this way can be related to each other in the form σH2 = C*σY2 *λ2 as predicted by stochastical theory (Gelhar,1993). Finally, we investigate which factors affect the residual error of the model estimation. Obviously, both transmissivity variations and errors in the head measurements are mostly responsible for a non-zero estimated residual head. Hence, the variances of head that are obtained from stochastically generated transmissivities and the intrinsic errors of the head measurements were determined. The results show that the stochastically predicted variances of the head are still somewhat lower than the variances of the residual head, indicating additional uncertainties in the fitted model. Indeed, the pumping rates turn out to be very evasive, as pumping rates in the study area are not always correctly reported from well owners. To investigate the effects of varying pumping rates on the residual head variance, 180 Monte Carlo simulations with randomly disturbed pumping rates of varying magnitudes (30 - 80 % of the reference value) are performed. The results show that pumping plays a smaller but still significant role for the estimation of the residual error, as the residual head variances obtained from stochastic pumping are lower than those obtained from the stochastic transmissivity field . 1 Department of Geohydraulics and Engineering Hydrology, University of Kassel, Kurt- Wolters Str.3, D34109 Kassel, Germany 2 Department of Water Resources Engineering, Chulalongkorn University, Bangkok, Thailand

Analysis of spatial–temporal patterns of water table change as a tool for conjunctive water management in the Upper Central Plain of the Chao Phraya River Basin, Thailand

A sustainable strategy for conjunctive water management must include information on the temporal and spatial availability of this natural resource. Because of water shortages in the dry seasons, farmers on the Upper Plain of the Chao Phraya River basin, Thailand, are increasingly using groundwater to meet their irrigation needs. To evaluate the possibilities of conjunctive water management in the area, the spatial–temporal changes in the water table of the Younger Terrace Aquifer were investigated. First, a regional geomorphological map based on field surveys, remote sensing and previous environmental studies was developed. Then, the well data were analyzed in relation to rainfall, streamflow, yield and pumpage, and the data were interpolated using geostatistical techniques. The results were analyzed via integrated zoning based on color theory as applied to multivariate visualization. The analysis results indicate areas that would be more suitable for groundwater extraction in a conjunctive management framework with regard to the natural hydrogeological processes and the effects of human interaction. The kriging results were compared with the geomorphological map, and the geomorphological areas exhibit distinct hydrogeological patterns. The western fans exhibit the best potential for the expansion of conjunctive use, whereas the borders of the northern fans exhibit the lowest potential.

Climate change’s impact on irrigation system and farmers’ response: a case study of the Plaichumpol Irrigation Project, Phitsanulok Province, Thailand

The Plaichumpol Irrigation Project, in Nan Basin of Thailand, is selected as a case study of impact study, where farmers depended on both surface and groundwater sources (especially in the dry year), to assess the impact on irrigation systems. The study used the MRI-GCM data to project the future climate condition and assess the impact on irrigation systems focusing on water shortage and groundwater pumping aspects in the selected consecutive dry years. The responses from farmers on the impact and adaptation were also gathered via site interviews and analyzed. Based on the bias-corrected MRI-GCM data, the annual rainfall in Nan Basin will decrease in the near future (2015–2039), compared with the past average data (1979–2006), while the rainfall will increase in the far future (2075–2099) compared with past. Water supply from dam will decrease in wet season and dry season, while water demand in both of near future and far future will increase in wet season and dry season. Less water shortage and groundwater pumping in both near-future and far-future periods are expected in the future consecutive dry years compared with the past, though the groundwater is still an important supplementary irrigation water source in the dry year. From the field interview, the farmers are ready to adapt to the changing situations and join in the water use meeting to follow up with irrigation officers about the adjustment of plant calendar and water allocation due to the climate change and to prepare adaptation measures as necessary.

Industrial Water Use Estimate in Bangkok Metropolitan Area and Its Vicinity

Abstract Water is essential to industrial development. Due to the groundwater control measures in the Bangkok Municipal Area and its vicinity, the actual amount of industrial water use needs to be assessed. The study proposes an estimation method of industrial water use in the area, using the existing registered data from the Ministry of Industry. With the derived water use unit for both domestic and processing purposes, the distribution of industrial water use by type and location in the study area can be derived. More industrial water demand was confirmed from the questionnaire survey and more groundwater wells tended to be developed to solve water deficit. Integrated water resources development and a more persuasive industrial water saving policy for the area need to be considered in order to cope with increasing industrial water demand and groundwater control policy.

Groundwater Recharge Study and Simulation — Kamphaeng Phet Case Study —

The feasibility of groundwater recharge scheme had been proposed to study in Kamphaeng Phet Province, about 400 km. north of Bangkok. The general movement of groundwater in the province was analysed and simulated from the data of the watertable monitoring program. Field experiment on artificial basin recharge was conducted and proved to be effective though sediment clogging issue was left to be solved. Water balance study from simulation results during the year 1997–2002 revealed that agricultural water use is the main reason for the decrease in groundwater table with the rate of 1–2 meters annually. To mitigate the situation, pumping control and/or groundwater recharge schemes are simulated and proposed in order to maintain the groundwater table as in the year 1997.

MECHANISM AND ESTIMATION OF SEDIMENTATION IN BANGKOK BAR CHANNEL

Mechanism of sedimentation in Bangkok Bar Channel in Thailand is investigated by using the periodically measured water depth around channel, dregded volume and the relation between discharged sediment concentration and discharged velocity measured at the river mouth of Chao Praya. Simple numerical simulations for predicting sedimentation volume in the channel are also carried out. The results show that both discharged sediment from the river and sedimentation around Bangkok Bar caused by waves and current play an important role in the sedimentation in the channel.

OIL SPILL MODEL IN RIVER BY FEM

ABSTRACT Oil spill accident may happen during oil loading/unloading or ship collision in the river. The prediction of oil spill spread is essential for environmental assessment and management. The study aimed to predict the spread distance of oil spilled in the river with tidal effect. The physical experiments with the scale of 1:700 were conducted to confirm the accuracy of empirical formula of oil spread in the calm sea suggested by Fay. The mathe matical model for oil spill prediction is developed where the river flow conditions are computed by finite element model based on the Saint-Venant equations and the oil spill movement is represented by one-dimensional Fay formula. The experimental results showed that Fays empirical formula can adequately represent oil slick movement even in moving water. The oil spread lengths in Chao Phraya River were then simulated by the developed model with various conditions in the year. From the study, the affected lengths of oil spill is in the range of 6–11 km and the convection transport is the main force to spread the oil slick. The study also showed the application of Finite Element Model in river environmental problem and in the environmental management.