xxxxx项目可研报告(英文版

xxxxx项目可研报告(英文版内容摘要：

aviya 8176。 49′22″N 80176。 45′24″E 19641991 28 448 Palampoddar 8176。 33′26″N 81176。 03′45″E 19441985 42 455 Pangurugaswewa 8176。 44′12″N 80176。 53′31″E 19571975 19 473 Pelwehera 7176。 54′12″N 80176。 40′30″E 19441989 46 529 Sigiriya 7176。 57′05″N 80176。 45′01″E 19441974 31 Table Rivergauge Station List Name Basin Location Period of Record Type of Gauge Latitude Longitude Year Month Huruluwewa Yan Oya 8176。 13′35″N 80176。 43′40″E Gauging Weir Illukwewa Yan Oya 8176。 20′10″N 80176。 44′05″E Staff Gauge Current meter Horowpothana Yan Oya 8176。 34′36″N 80176。 52′42″E do Pangurugaswewa Yan Oya 8176。 44′55″N 80176。 52′45″E do Wahalkada Thawalam Halmillewa Oya 8176。 43′36″N 80176。 51′05″E do Yakawewa Ma Oya 8176。 43′25″N 80176。 40′50″E do Feasibility Study of Yan Oya Reservoir Project in Sri Lanka Chapter 2 China CAMC Engineering Co., LTD. 9 Runoff Runoff Characteristics The watershed runoff is formed mainly by precipitation, but also influenced by the irrigation return flow from 3867ha farmland on both sides of the lower reach in the basin Huruluwewa range. The change for runoff and rainfall in temporal and spatial is synchronous on the whole. The mean annual runoff depth highest value is in 1984 and the lowest one is 25mm in 1988. The ratio of runoff in wet years to that in dry years is . Annual distribution of runoff shows significant changes in peak and valley and obvious seasonal nature because of monsoon. Runoff peaks occurred in December, which were caused mainly by the northeast monsoon and accounts for about 35% of annual runoff. Besides, the dry season is usually between March and September, of which the fourmonth total runoff from June to September account for only 5% of annual runoff. The driest month runoff accounts for less than 1%, which usually occurs in June and July. The mean annual distribution of runoff above Yan Oya dam site is shown in Table 23 and Figure 21. In terms of space, it is generally considered that precipitation gradually increases from southwest to northeast due to the northeast monsoon which is in line with the river walk. The spatial variation of runoff is also followed by this rule which can be shown clearly from the mean annual isohyets in the annexure figure SYS201. Table Mean Annual Distribution of Runoff above Yan Oya Dam Site Basin Name Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Mean Discharge (m3/s) Total Runoff (104m 3) 5222 1723 1041 783 545 204 179 384 269 1260 3479 8170 23260 Runoff Depth (mm) Distribution ratio (%) 22 7 4 3 2 1 1 2 1 5 15 35 100 Feasibility Study of Yan Oya Reservoir Project in Sri Lanka Chapter 2 China CAMC Engineering Co., LTD. 10 1 2 3 4 5 6 7 8 9 10 11 12MonthRunoff Depth (mm) Figure Mean Annual Distribution of Runoff Histogram above Yan Oya Dam Site Basin Runoff Yield Computation Total drainage area of Yan Oya catchment at proposed dam site is 1341km2. The basin above dam site can be divided into three sub catchments, namely Yan Oya catchment upto Huruluwewa, intermediate catchment from Huruluwewa upto Horowpothana and intermediate catchment from Horowpothana upto Pangurugaswewa. In the present study, because the Huruluwewa has been built and run, it is considered that Yan Oya cathment upto Huruluwewa influences the runoff at dam site only by the irrigation return flow from 3867ha farmland on both sides of the lower reach in the basin Huruluwewa downstream range. Therefore, the other two sub catchments can be separately considered and added up to obtain the runoff at the proposed dam site. The runoff record at Horowpothana has been revised, which has 41 year record from 1951 to 1991. It is representative for intermediate catchment from Huruluwewa upto Horowpothana. According to the similarity between intermediate catchment from Horowpothana upto Pangurugaswewa and the adjacent MaOya basin in the climate and Feasibility Study of Yan Oya Reservoir Project in Sri Lanka Chapter 2 China CAMC Engineering Co., LTD. 11 geographical conditions, the runoff in the region can be solved by using rainfallrunoff model. Thereby it can be obtained that 41 year record of average monthly runoff from 1951 to 1991 at the proposed Yan Oya dam site which is given in table average annual discharge is annual discharge runoff depth . The 41 year mean annual discharge from 1951 to 1991 is be puted by frequency analysis. Pearson III curve is adopted to fit the curve, whose parameters is namely Q =， Cv= and Cs/Cv=. The design mean annual discharge in different reliability of 10%, 50%, 90% are respectively , Feasibility Study of Yan Oya Reservoir Project in Sri Lanka Chapter 2 China CAMC Engineering Co., LTD. 12 Table Mean Monthly Discharge (m3/s) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Average Annual Yield （ MCM） 1951 33480 1952 30280 1953 9760 1954 30000 1955 14960 1956 7730 1957 66550 1958 21300 1959 12970 1960 16360 1961 38520 1962 16520 1963 66240 1964 12070 1965 28070 1966 35500 1967 29380 1968 11810 1969 29410 1970 28240 1971 32270 1972。