http://www.paper.edu.cn 45 Journal of Hydrodynamics, Ser. B ,3 (2002) ,54 - 59 hina Ocean Press, Beijing - Printed in China FIELD INVESTIGATION OF TEMPERATURE AND DO OF THE ERTAN RESERVOIR D URING OPERATION PERIOD Jiang Hong State Key Hydraulics Laboratory of High Speed Flows , Sichuan University , Chengdu 610065 , China Xie Guang2wu , Lu Hong2wei Chengdu Hydropower Institute of Design and Investigation , Chengdu 610072 , China Luo Lin State Key Hydraulics Laboratory of High Speed Flows , Sichuan University , Chengdu 610065 , China (Received Apr. 15 , 2001) ABSTRACT : The Ertan hydropower station at the Yalong Riv2 key issue to impact the aquatic organism. It is almost er of Southwest Sichuan Province. It is one of the biggest in2 impossible to investigate the DO problem in an indoor stalled capacity hydropower stations in China. The main stream experiment. And mathematical simulation , if any, reservoir length reaches 145km and the branch Ganyu River must be supported by a solid data set. The DO distri2 reaches 40km under normal storage level. The reservoir surface bution data represented here can be used to help for covers 101km2 area , and has 5.8 billonm3 capacity. It began wa2 understanding of similar projects of DO issue , and as a ter storage since May 1998. The first generator was in operation in August 1998. The project was finished at 2000. The Ertan fundamental calibration data set. reservoir is a typical riverway style one. In order to understand The Ertan reservoir is a typical riverway style 3 the thermal effect , Dissolved Oxygen (DO) distribution and out2 one. Its total storage capacity is 5. 8 billion m , and let flow temperature under reservoir storage condition , three field regulating storage 3. 37 billion m3 , Mountains are measurements were carried out in January, April , and July of around the reservoir that distance from the water sur2 2000 , respectively. The measured results are analyzed in the pa2 face about 1500m. Average width of main stream of per. The results will provide reserchers a valuable data set for cal2 the reservoir is about 400m , and up to 1000m width at ibration of mathematical model and realistic understanding for some reach of the branch Ganyu river. The backwater stratified flow issue and DO profiles in a large scale deep reser2 zone of the main stream Yalong River is 145km, and voir. the branch Ganyu River 40km , at the highest storage KEY WORDS : reservoir , temperature , DO , field measure2 level - 1200m, respectively. The reservoir surface 2 ment area is 101km under this level. 1. INTROD UCTION[ 1～4] 2. TEMPERATURE AND DO OVERVIEW BE2 Stratifed flow occurs usually in deep reservoir. FORE THE RESERVOIR BUILT[ 5] This issue plays a very important role in aquatic ecosys2 2. 1 Temperature tem of the water body. Investigation for thisphenome2 According to statistics of the measurement data na is an interesting topic for both environmental and acquired from the Xiaodeshi hydrological station , hydroelectric engineers. A few theoretical case studies which is 12km downstream from the Ertan dam site , were carriedout , such as 2D , or even 3D , mathemati2 during 1960～1962 and 1988～1997 , the multi2year2 cal simulation for the thermal stratification. Physical averaged month2average temperature was 10. 5°C ; the model investigation for this kind of flow is too expen2 highest month2averaged temperature is 19. 5°C , which sive , and the experiment results is not good enough for appeared in August , and it was almost the same as that calibration of the mathematical model due to its size in June andJuly; the lowest month2averaged tempera2 limit. A full size field investigation of a typical large ture appeared in January , is 8.4°C. scale deep reservoir will provide researchers a conve2 2. 2 DO nient approach to calibrate their mathematical models , The monitoring periods at the Xiaodeshi hydro2 and realistic understanding for the stratification in the logical station for DO were 1973～1979 , 1981 , 1989 reservoir. and 1990. The Multi2year2averaged DO value is 7. DO profiles in large scale deep reservoir is another 8mg/L. The highest DO value of the measured data 转载 中国科技论文在线 http://www.paper.edu.cn 55 appeared in 1981 , was 8.8mg/L. The lowest value of tween surface and bottom of the reservoir in winter DO appeared in 1973 and 1977, was 7. 3mg/L. The was 3. 7～4. 9°C. variation, under which is unstable , occurred in Jan2 uary , April , August and December of each year due to combination effect of hydrologic , climatic and temper2 ature factors. In remained period DO was stable , and changed small. 3. FIELD MEASUREMENT OF TEMPERATURE AND DO 3. 1 Set up of sampling point To ensure the accuracy of the sampling cross sec2 tions, each monitor section is chosen from the existed sediment cross section and field investigation. Eleven monitor sections were chosen in the main stream. Their positions are shown in Table. 1 (a) Longitudinal temperature profiles in winter 3. 2 Measurement f requency The measuring time were September 24 ～ 26 , 1999 , January 13 ～ 17, 2000, April 14 ～ 16 , 2000 and J uly 24～25 , 2000 , respectively. 4. MEASUREMENT RESULTS AND ANALYSES 4. 1 Data assembly Acquired data were inputted into computer imme2 diately after each field measurement , and were re2 viewed by assigned person. The obtained data were processed by meansof Excel for statistics , data gather2 ing , tabulation , and plotting. 4. 2 Results and analyses 4.2.1 Temperature The measurement results are as follows: 1 (b) Vertical temperature profiles in winter Fig. 1 Winter temperature profiles (1) Winter results The longitudinal and vertical temperature profiles in winter are shown in Fig.1. From the figures it can (2) Spring results be seen that : The longitudinal and vertical temperature profiles The temperature near the dam was obviously in spring are shown in Fig.2. higher than expected. According to the measured From the figures it can be seen that : reservoir end temperature and the increasing rate of Estimating from the measured reservoir end tem2 ° temperature in winter , 0. 0125°C/ km, the tempera2 perature , 14.3 C, and the increasing rate of tempera2 ° ture near the dam should be 9.0°C. But the measured ture in spring, 0. 011 C/ km, the temperature at the temperature near the dam was 9.9～ dam site before the project construction should be 15. ° 13. 5°C, higher than estimated; 7 C. The measured temperature near the built dam 9. ° ～ ° Due to the low entrance rate at the reservoir end 7 C 17. 8 C , and stratified flow was observed. in winter ( measured rate was 549m3/ s) , the inflow Since the reservoir end temperature change con2 had small contribution to the reservoir temperature dis2 tributed to the temperature structure increased , even ( 3 tribution structure , which was limited within 35km the entrance flow rate was still small 516m / s at mea2 range from the end; sured time) , the disturbed range expanded to 70km The measured data represented that stratified flow from the end; occured even in winter. The thermocline was in the Stratification happened obviously in spring too , ～ range of 1171. 7m～1121. 7m, or 20m～70m below and the thermocline was in 1181. 5m 1111. 5m the surface. The temperature gradient of the thermo2 range , or 70m below and to the surface. The temera2 ° cline is 0. 1°C/ m; and the temperature difference be2 ture increasing rate was 0. 12 C/ m; and the tempera2 中国科技论文在线 http://www.paper.edu.cn 65 ture difference between the surface and the bottom ranged from 1.3°C～8. 6°C. 3 (b) Vertical temperature profiles in summer 2 (a) Longitudinal temperature profiles in spring Fig. 3 Summer temperature profiles perature in summer , 20.1°C, and the increasing rate , 0. 004°C/ km , the dam site before the project construc2 tion should be 20. 6°C. After the dam is built, the temperature near the dam was 16. 0～25. 0°C , ther2 mocline occured ; The entrance flow rate was large ( measured rate was 2279m3/ s) . The temperature at the reservoir end contributed the temperature structure of the reservoir arlgely, up to 90km from the end and 10m below the surface ; The thermocline ranged from 1182.6～1172. 6 m , or the surface to the 10m below the surface. The temperature gradient was 0. 38°C/ m～0. 60°C/ m. The 2 (b) Vertical temperature profiles in spring Fig. 2 Spring temperature profiles layer below the 10m depth still had some gradient ; The temperature difference between the surface and the bottom was in 6.1°C～9. 7°C range. (3) Summer results 4. 2. 2 Measured results of the dam downstream The longitudinal and vertical temperature profiles The Xiaodeshi hydrological station is located at in sunmer are shown in Fig.3. 12km downstream from the dam. Its temperature change reflects the change before and after the dam built. The long term temperature recordsof the station before and after the reservoir storage are collected. There were 13 years temperature records at the station before the reservoir storage , including 1960～1962 and 1988～1997. The temperatures are shown in Table 2. Since the reservoir storage , May 1998 , the tempera2 ture records are June 1998 and whole year of 1999. They are also shown in Table 2. From Table 2 , it can be seen that: (1) From October to January next year after the temperature of the dam downstream grew obviously than that before the storage. Because the water retain2 ing time in the reservoir in winter and fall seasons is 3 (a) Longitudinal temperature profiles in summer longer than that in natural condition , the water body From the figures it can be seen that : in the above period can obtain more energy , the temp2 Estimating from the measured reservoir end tem2 中国科技论文在线 http://www.paper.edu.cn 75 Table 1 Monitor sections in the main stream unit :km Golden Dam River Item Front No.7 No.10 No.13 No.15 No.17 No.20 No.24 No.30 No.34 Bridge (DF) ( GRB) Dist .