Seasonal Pattern of Mean Monthly Rainfall. Battambang Stung Sanker Treng Stung Sanker Pursat Stung Prusat Kompong Speu Prek Thnot Takeo Slakou

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1 Figures

2 LEGEND 5 Study Area Pursat Catchment Area Meteorological Station(1) Rainfall Station(6) Water Level Gauge(1) Kanpong Chhnang 5 6 1,549m E l e Sangkea Satob Phnom Penh p h a n t M o u 971m Prek Thnot Peam Kley Kirirom 4 Kampong Speu Phrum Sruoch 724m 2 Sea n t a i Stung Chral n s 838m Slakou River Study Area Takeo 3 Figure B-1 Location of Meteorological Station and Water Level Gauge Station B - F1

3 B - F2 Figure B-2 Isohyetal Map TBENG MEAN CHEY SISOPHON STUNG TRENG SIM REAP BATTAMBANG KOMPONG THOM PURSAT KAMPONG CHAM KOH KONG SIHANOUK VILLE TAKEO PHNOM PENH SVAY TEAP Source: Annex A Hydrology of Final Report for Irrigation Rehabilitation Study in Cambodia Mekong Secretariat, June BANLUNG SENMONOROM km

4 Seasonal Pattern of Mean Monthly Rainfall Rainfall (mm) Battambang Stung Sanker Treng Stung Sanker Pursat Stung Prusat Kompong Speu Prek Thnot Takeo Slakou 5.. Jan. Feb. Mar Apr May Jun Jul Aug Sep Oct v Dec Station Jan. Feb. Mar Apr May Jun Jul Aug Sep Oct v Dec Annual * Annual# Period of Record Battambang Treng Pursat Kompong Speu Takeo *: Mean of annual rainfall values #: Sum of mean monthly rainfall Source: Data were derived from Annex A Hydrology of Final Report for Irrigation Rehabilitation Study in Cambodia, Mekong Secretariat June Figure B-3 Seasonal Pattern of Monthly Rainfall of Long Term Period in Low Land B - F3

5 Comparison of Monthly Average Rainfall Patterns between Lowland and Mountainous Area 35. Monthly Rainfall (mm) Average in low land*1 Kirirom Month Correlation of Monthly Mean Rainfall between Lowland and Mountainous Area Monthly Rainfall in Mountainous Area (mm) y = 1.49x Monthly Rainfall in Lowland (mm) Unit:mm Year Jan. Feb. Mar Apr May Jun Jul Aug Sep Oct v Dec Annual Average in low land* Kirirom te: Average rainfalls for four years from 1966 to *1 : Average of those at Kampong Spueu and Phnom Srouch Figure B-4 Seasonal Patterns of Monthly Average Rainfall at Lowland (Kompong Spueu and Phnom Srouch) and at Mountain Area (Kirirom) B - F4

6 Spacial Correlation of Monthly Rainfall Prey Kabas Kirivong Angkor Borey Somrong Bati Koh Andeth (mm) Takeo (mm) Monthly Rainfall in Takeo Province in 2 Unit:mm Name of Station Jan. Feb. Mar Apr May Jun Jul Aug Sep Oct v Dec Annual Distance from Takeo Takeo Prey Kabas km north-east Kirivong km south Angkor Borey km east Somrong km north Bati km north Koh Andeth km south east Source: MOWRAM, Takeo Figure B-5 Spacial Correlation of Monthly Rainfall in Low Land in Takeo Province B - F5

7 Figure B-6 Slakou River System 8 B - F Tumnup Lok Reservoir 4 Don Krouch Stream Phe Stream T r a s S t r e a m 332km 2 O Saray Reservoir 51km 2 137km Slakou River M Main Canal. 1 ain Canal. 2 Main Canal. 3 Kpob Trobek Reservoir ,2km 2 at Thnot Te Reservoir Thnot Te Reservoir Krachab-Chrouy Samraong Reservoir Kanlaeng Reservoir Takeo O' Tom Reservoir

8 Rating Curve at Slakou Upstream (Tumnup Lok Reservoir Site) y = 13.52x R 2 =.9844 Dsicharge (m 3 /sec) Water level, x (m), x= reading by automatic water level recorder minus.15 m Rating Curve at Slakou Downstream (National Road.3 point) Discharge (m 3 /sec) y = 13.65x R 2 = Water level (m) Figure B-7 Rating Curves for the Slakou Upstream (Tumnup Lok Reservoir Site) and the Slakou Downstream (National Road. 3) B - F7

9 Flow Measurement Records N Date H=m Q=m3/sec 1 16-Jan Feb Dec Feb Jan Jan Mar Aug Sep Dec Sep Oct Sep Oct Sep Oct v Apr Oct Oct v v v Oct Oct Discharge in m3/sec Rating Curve of the Prek Thnot at Peam Kley for High Flow more than 2.3 m in water level y = 2.891x x R 2 = Water level in meters Low Flow Records N Date H=m Q=m3/sec 2 16-Jan Rating Curve of Prek Thnot at Peam.96 Kley 3 28-Feb for Low Flow less than 2.3 m in water 1.8level 4 15-Dec Feb Jan Jan Mar y = 12.85x x Aug R 2 = Discharge (m3/sec) Water level (m) Figure B-8 Discharge Measurement Records and Flow Rating Curves of Prek Thnot River at Peam Kley B - F8

10 Comparison of Rainfall and Runoff in the Prek Thnot River Basin Rainfall Runoff Potencial ETo 2. (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct v Dec unit: mm Item Jan Feb Mar Apr May Jun Jul Aug Sep Oct v Dec Rainfall Runoff Potencial ETo Rainfall and runoff are averages for four years from 1966 to ETo was estimated by the modified Penman. Figure B-9 Comparison of Monthly Rainfall and Runoff in the Prek Thnot River Basin B - F9

11 Year and Month Discharge (m3/sec) Rainfall (mm) Rainfall (mm) Actual (m3/s) Simurated (m3/s) in The Slakou River Basin,The Kingdom of Cambodia Figure B-1 Comparison between Actual Runoff and Simulated Runoff by Rainfall Distribution Method in Prek Thnot River B - F1

12 Flood discharge (m3/sec) Hydrograph of Year Flood at Kpob Trobek Reservoir Total KpobTrobek Reservoir Time hr Sub-Storm Total Time (hr) Flood (m3/sec) Hydrograph of Year Flood at O Saray Reservoir Total Time (hr) O Saray Reservoir Time hr Sub-Storm Total Flood Discharge (m3/sec) Hydrograph of Year Flood at Tumnup Lok Reservoir Tumnup Lok Reservoir Time hr Sub-Storm Total Time (hr) Figure B-11 Year Probable Sub-storm Hydrographs and Composite Hydrograph at the Three Reservoirs B - F11

13 E Dike Top EL. : 3 Dike Top EL. : 39.m H.W.L : 37.3m Dead Storage (.685 Dead Storage (.274MCM) after 2years 25 2 H.W.L : 38.3m Volume(MCM) Area(ha) Gross Capacity : MCM(Dike Top EL. : 39.m) Gross Capacity : MCM(Dike Top EL. :4.m) Dike Top EL.(4.5m) Volume(MCM) Area(ha) 4. El e v H.W.L : 38.92m Gross Capacity :.328 MCM(Dike Top EL. : 4.5m) 38.5 Dead 38. Storage ( Dead Storage 37. (.12 MCM) 36.5 after 2years Area (ha) Elevation (m) H.W.L : 41.3m Dike Top EL. : 2 Dike Top EL. : 43.m H.W.L : 42.3m Dead Storage (1.66 MCM) after Dead Storage (.664 MCM) after 2years Volume Tumnup Lok Reservoir Volume(MCM) Area(ha) Gross Capacity : 1.66 MCM(Dike Top EL. : 43.m) Gross Capacity : 3.3 MCM(Dike Top EL. :44.m) Figure B-12 Storage Volume and Area Curves of Kpob Trobek, O Saray &Tumnup Lok Reservoirs B - F12

14 Water Balance Calculation in Single Reservoir to (n + 1) S n-1 + IN n IWR n > S n-1 + IN n EV n P n IWR n > ESC S n = ESC SPIL n = S n-1 + IN n EV n P n IWR n - ESC DF n = S n-1 > S n = S n-1 - (EV n + P n) SPIL n = DF n = IWRn + Pn +EVn - Sn-1 - INn Sn = Sn-1 + INn EVn Pn IWRn SPILn = DF n = S n = - (EV n + P n) SPIL n = DF n = IWRn + Pn +EVn - Sn-1 - INn S: storage volume IN: inflow EV: evaporation loss from reservoir P: percolation loss from reservoir IWR: irrigation water requirement ESC: effective storage capacity SPIL: outflow from spillway DF: deficit volume n: end of objective half a month n-1: end of previous half a month to (n + 1) Water Balance Calculation in Connection of Two Reservoirs SPC n = ESC - S n-1 - IN n - IWR n SPCn (SPC: space to store water in receiving-side reservoir) PSS n = S2n-1 + IN2n - EV2n - P2n PSS n (PSS: Possible supply volume by supply-side reservoir) to (n + 1) SPCn > PSSn S2n-1 + IN2n - IN21n > S2n-1 + IN2n - IN21n EV2n P2 n > ESC2 S2n = ESC2 SPIL2 n = S2 n-1 + IN2 n - IN21 n EV2 n P2n - ESC2 IN21 n = SPCn IN21 n = PSS n S2 n-1 > S2n = S2n-1 - EV2n - P2n SPIL2 n = S2n = S2n-1 + IN2n - IN21 n EV2n P2n SPIL2 n = S2 n = - EV2 n - P2 n SPIL2n = Supply-Side Reservoir S2: storage volume IN2: inflow from own stream IN21: flow from supply side reservoir to receving side reservoir EV2: evaporation loss from reservoir P2: percolation loss from reservoir ESC2: effective storage capacity SPIL2: outflow from spillway n: end of objective half a month n-1: end of previous half a month Sn-1 + INn + IN21 IWRn > S n-1 + IN n + IN21 EV n P n IWR n > ESC Sn = ESC SPIL n = Sn-1 + INn + IN21n EVn Pn IWRn - ESC DF n = S n-1 > S n = S n-1 - (EV n + P n) SPIL n = DF n = IWR n + P n +EV n - S n-1 - IN n - IN21n Sn = Sn-1 + INn + IN21 EVn Pn IWRn SPILn = DF n = S n = - (EV n + P n) SPIL n = DF n = IWRn + Pn +EVn - Sn-1 - INn - IN21n S: storage volume IN: inflow from own stream EV: evaporation loss from reservoir P: percolation loss from reservoir IWR: irrigation water requirement ESC: effective storage capacity SPIL: outflow from spillway DF: deficit volume n: end of objective half a month n-1: end of previous half a month Receiving-Side Reservoir Figure B-13 Chart of Water Balance Calculation Process B - F13