1975 T Ft..277Q Salt Water Intrusion
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AQNCY FOR INi'KRNATIONAL DEVELOPMCNT FOR AID USE ONLY W.AIHIN TON. 0. C.205 3 BIBLIOGRAPHIC INPUT SHEET -a A. PRIMARY 1. SUBJECT Science and technology TCOO-0000-G750 C'LASSIt FICATION * Applications--Thailand SlAAY 2. TITLE AND SUBTITLE Salinity intrusion and flood control investigation for Bicol RiverBatn 3. AUTHORIS) Ackermann,N.L.; Tingsanchali,Tawatchai; Sahagun,V.A. 4. DOCUMENT DATE s. NMBER OF PAGES 6. ARC NUMBER 1975 T ft..277Q ARC 7. REFERENCE ORGANIZATION NAME AND ADDRESS AIT a. SUPPLEMENTARY NOTES (Sponsoring Organization, PubliIherap Availabllity) (InATT research rpt.no.51) 9. ABSTRACT 10. CONTROL NUMBER IIl PRICE OF DOCUMENT 12. DESCRIPTORS 13. PROJECT NUMBER Bicol River' Thailand Flood,control 14. CONTRACT NUMBER Hydrology AID-492-834 Salt water intrusion Is. TYPE OF DOCUMENT AID 890.1 (4.741 AslanAAlT Institute of Technology Bangkok Thailand research report. 'No. 51 SALINITY INTRUSION AND FLOOD CONTROL INVESTIGATION FOR BICOL RIVER BASIN by Norbert L. Ackermann Tawatchal Tingsanchali Virgillo A. Sahagun In cooperation with Conducted for BICOL RIVER BASIN COUNCIL US/AID Philippines as represented by Contract No. AID 492-834 National Hydraulic Research Center National Irrigation Administration Bureau of Pu *Ilc Works Bangkok, Thailand May 1975 SALINITY INTRUSION AND FLOOD CONTROL INVESTIGATION FOR BICOL RIVER BASIN by Norbert L. Adcormann Profssor of Water Resources Engineering Tawatchai Tinganchali Assstant Remrch Professor Virgillo A. Shagun Senior Research Associate DIVISION OF WATER RESOURCES ENGINEERING ASIAN INSTITUTE OF TECHNOLOGY Bangkok, Thailan May 1975 In a previous study oonduted Iby the Aeian: Insitute of Tec Ihino ogy, the effeot of varioue.food controt alternatives on food Zeve.s throughout the Bicol River Basin were deterined. This infovation is provi-ed fn Volumes I and II of the, AXT Reaearch Report No. 48. BicoZ River Basin Flood Contro Inveatigation, (7). Xn that repor-jten flood controZ measures were desoribed in term of their ability to provide effective flood reZief for 'design storme having IS3 and 50year return pqrOd. Other ombinations of food control meaeures in corunotion with various irrigationwithdrawal rates were later identified as worthy offurher investgation. In the present audy those flood contro measures ".denttf[ed as deserving frther, invetigation are analyxed in tems of their-effectivene in reduroi water surface.ZeveZ in the Bicol and Stpocot Rivers. Effeots of impementing various flood oontroZ measures on saZinity intrusion into these -river is aso:studied as weZ as-,the effects of various proposed fZood relief measurea on lon term' drainage in the upper reaches of the Bico River. TABE OF CONTENS CHAPTER" TITLE PAGE Preface i ITabe of Contents ii List of Figures iv List of Tables vi INTRODUCTION 1 1.1 Location and Description 1 1.2 Flood Control Measures 3 1.3 Flood Drainage from Upper Reaches of Bicol River 4' 1.4 Salinity Intrusion 5, II EFFECT OF FLOOD CONTROL MEASURES ON RIVER STAGES 6 2.1 Description of Basin Modifications 6 2.2 Effect of Basin Modifications on River Stages 8: III LONG TERM DRAINAGE IN UPPER REACHES OF BICOL RIVER 21 IV SALINITY INTRUSION 26 4.1 Introduction 26 4.2 Basis of Mathematical Model of Salinity Distribution 28 - Salt Balance Equation, 28 - Hydrodynamic Equations 30 - Coupling of Salt Balance and Hydrodynamic Equations 31 - Finite Difference Scheme 32, 4.3 Construction and Investigation of Hydrodynamic a -linity Models tor Bicol and Sipo ivers 32 - Model Construvn 33 - Boundary Conditions 34 - Initial Conditions 38 - Quasi-Steady Computation 39 - Model Study 39 4.4 Model Application 45 - Tidal and Hydrological Conditions 45 - Roughness Coefficients and Diffusion Constants 45, - Basin Nodifications - Present System with No Other Modification.s,46 TAXLE OF CNTENhS:1ACMrriIED) CHAPTER TITLE, PAGE, - Present System with Cutoff no.3 46. - Present System with Withdrawal at. Bicol-Ragay Diversion 47 - Present system with Cutoff no.3 and. Withdrawal at Bicol-Ragay Diversion" 48 4.5 Discussions 54 V SUMMARY AND CONCLUSIONS 60 Flood Peak Reduction 60 Long Term Drainage 60 Salinity Intrusion 63 REFERENCES 65 -LIST OF FIGURES 4FIGURE TITLE PAGE 11 The Bicol River Basin 2 2.1 Changes in Water Surface Levels at Lake.Bato'due to Flood Control Measures 11 2.2 Changes in Water Surface Levels at Ombao due to Flood Control Measures 12 2.3 Changes in Water Surface Levels at Naga Cityrdue. to Flood Control Measures 13 2.4 Changes in Water Surface Levels at Libmanan-due to Flood Control Measures 14 2.5 Discharge Hydrograph for Sipocot-San Miguel Diversion 15 2.6 'Changes in Water Surface Levels at Libmanan due to Flood Control Measures 16 2.7 Changes in Water Surface Levels at Naga City due to Flood Control Measures 17 2.8 Changes in Water Surface Levels at Ombao due 'to Flood Control Measures 18 2.9 Peak Water Surface Profiles along Bicol and Sipocot 'Rivers for 13 Year Flood 19 20( Peak Water Surface Levels at Libmanan, Naga City, Ombao and Lake Bato for Flood Control Measures for 13 Year Flood 20 3.1 ! Water Levels at Libmanan, Naga City, Ombao and Lake Bato Affected by Channel Deepening 23 3.2 Water Levels at Nodes 16 through 19 as Affected by Channel Deepening 24 3.3 Water Levels at Node 20 and SI Affected by Channel Deepening 25 4.41 Node and Branch Schematization for Bicol and Sipocot Rivers. Bicol River Basin 35 4.2 Constant Fresh Water Inflow to Nodes, Bicol and Sipocot Rivers 36 4.3. Water Level and Salinity Boundary Conditions and .Corresponding River Discharge at Bicol River Month for Existing River System (No Flood Control Scheme) 37 LIST OF 'FIGUES (cONTIuED) CHAPTER TITLE -PAGE 404 Discharge, Water Level and Salinity at Libmanan for!'Existing River System (No Flood Control Scheme) 41 4.5 Discharge, Water Level and Salinity at Cuyapi for Existing River System (No Flood Control Scheme) 42 4.6 Discharge, Water Level and Salinity at Naga City for Existing River System (No Flood Control Scheme) 43 4.7 41aximum and Minimum Salinity Distributions along Sipocot and Bicol Rivers for Existing River System (No Flood Control Scheme) 44 4.8 Discharge, Water Level and Salinity at Libmanan for Various Flood Control Measures 49 4.9 Discharge, Water Level and Salinity at Cuyapi :for Various Flood Control leasures 50 4.10 Discharge, Water Level and Salinity at Naga City for Various Flood Control Measures 51 4.11 Salt 'Water Intrusion along Bicol River and Maximum' Possible Salinity at Naga City 52 4.12 Salt Water Intrusion along Sipocot River and Maximum Possible Salinity at Libmanan 53 4.,13 Maximum Salinity Distribution along Sipocot and .Bicol Rivers for Various Flood Control Schemes 58 4.14 Minimum Salinity Distribution along Sipocot and Bicol Rivers for Various Flood Control Schemes 59 - V, LIST OF TABLiS TABLEi TITLE PAGE- 2.1 Description of Flood Control Systems 7 2*2 1Effectiveness of the Various Flood Control Measures in Chanfina Flood Peak Level (13-year Flood) 9 2.3 Effectiveness of the Various.Flood Control Measures irA Changing the 11-day Average River- Stage Following the Flood Peak (13-year Flood) 10 Summary Table I 61 Summarv Table II 62 Summary Table III 64 I. INTRODUCTION,," 1.,1 Location and Description The Bicol River Basin is located in the lower portion of the Island of Luzon extending from 1220451 to 123040' east longitude and from 130001 to 14000' north latitude. Situated about 400 km. from the city of Manila , the basin embraces the central portion of the Province of Camarines Sur, the northern portion of the Province of Albay and a small portion of th( Province of Camarines: Norte. The basin as shown in Fig.l.l is an elongated flat plain b6rdered by a chain of mountains and volcanoes at the eastern side and highlands and low hills on the western side.. It-covers-an area of 3120 sq.km. and extends in northwest-southeast direction approximately 135.km. with!a maximum width of 35 km. The basin's principal waterway is the. Bicol River which originates at Lake Bato and meanders generally in a northwestwardly direction-until it meets " the Sipocot River coming from the north. From the confluence of these !two rivers, the Bicol widens considerably as it travels in a northeast directibn to its outlet at San Miguel Bay. the main tributaries of the: Bicol River are the Quinali, San Agustiin, Irraya and Pawili Rivers, while tnose or the Sipocot River from the north are the -ulantuna, Culacling !and Yabu Rivers. The three lakes in the.basin - Lakes Baao,'., Buh, .and Bato, a provide tributary,; flow into ,the Bicol'River. The scenic Mayon Volcano is also w ithin the basin.*. 2 W+ool .'. .' . ' A.-.. 1I PULANTUNA RESE R.~ .. * ....... MANI AN MIGUE BAY. G:Itulf .G CITY LOCATION MAP % ""'",oPill|; I ego Basin Boundary "O AraS e t Flodn Proposed Flood Control 5 0 a 10 15 20OKW8. Fig.1.1:, Thl icol Rver Basin 1.2 Fl',od .,Control Measures Six modifications to the river system in the Bicol River Basin were proposed as measures which would serve to reduce river stages during periods of flood. The suggested modifications shown in Fig.ll are (U) Pulantuna Reservoir, (2) Sipocot Diversion, (3)Tidal Barrier, (4) Cutoff Channel no.3, (5)Bicol Diversion, and (6)Channel Deepening, The effectiveness of the following 10 systems of basin modifications designed to reduce river stages were reported by Ackermann, et al: (1975). (i) Pulantuna Reservoir (i) Sipocot San Miguel Diversion (iii) Tidal Barrier (iv) Cutoff no.3 (v) Bicol Ragay Diversion (vi) Channel DeeDeninr (vii) Tidal Barrier + Pulantuna Reservoii (viii) Bicol-Ragay Diversion + Pulantuna Reservoir + Pulantuna Reservoir (x) Bicol-Ragay Diversion + Tidal Barrier + Sipocot-San Miguel Diversion + Pulantuna Reservoir The <followingadditional combinations of flood control measures were identified as deserving further investigation and are considered in the • present study.