“五江一河”的洪水特征及其对跨流域调水量的制约——三评“红旗河工程”构想

在上文阐明"五江一河"径流量的年际变化及各节点具体径流量要比"红旗河工程"构想少得多的基础上,本文依据前人资料和成果,进一步阐述这些河流的径流量,在年内分配的不均匀性与洪水特征,及其对跨流域调水量的制约作用。研究表明:"五江一河"在11月到翌年4月,径流量只占全年总径流量的12.09%~21.84%,月均只有2.01%~3.64%,为冬、春季枯水期。其径流量只比拟调水比例20%或21%的月均值1.67%或1.75%略多。如此之少的水量,只能维系流域内的生态、生产及生活用水,而不能跨流域调水。何况"红旗河"中、下游在冬季结冰期也难以进行调水。每年6月份到9月份的4个月,"五江一河"径流量占全年径流量的53.3%~88.3%,甚至8月份的月径流量可达全年总径流量的17.8%~29.6%,属于汛期。根据径流量的实际数据,一年当中可供调水时间段只有丰水与平水期的6个月或汛期的3~4个月,要比"红旗河工程"构想的全年调水的时间大大缩短。在可资跨流域调水的每年5—10月份的时间窗口中,如果按原构想的月均调水流量占年径流量的比例1.67%(按20%计)或1.75%(按21%计)进行调水,则"五江一河"的年调水总量仅为153.25×10^8m^3(按20%计)或161.50×10^8m^3(按21%计)。仅为原构想调水量600亿m^3的1/4,充其量不足27%。在丰水与平水期的6个月中实现年径流量20%或21%的年调水比例,就意味将月调水比例从占年径流量的1.67%或1.75%增加为3.33%或3.50%。这样,"五江一河"的年调水总量可达到306.50×10^8m^3或323.00×10^8 m^3。此调水方案,导致调水河道截面积或工程规模增加一倍,但调水量也只有原构想的大约一半或至多54%。如果将调水目标强行设定为600亿m^3,那么"五江一河"的调水比例将提高到占年径流量的27.1%(南水北调西线工程开展前),或除金沙江和雅砻江之外的其它调水河流的39.0%(南水北调西线工程完成后),"红旗河"的建设规模势必大大增加,这也意味着工程难度大大增加,意味着工程建设与运行成本大大增加,意味着洪水、地震与地质灾害的危险性大大增加。"五江一河"实际可调水量比"红旗河"构想严重减少,使人不禁会对"红旗河"工程立论的科学基础和科学依据提出质疑。

The Flood Characteristics of “Five-Jiang and One-He Rivers” and Its Restriction on Inter-basin Water Transfer: The Third Comment on the “Hongqi River Project” Conception

The paper“How Much Water Can be Inter-basin Transferred from‘Five-Jiang and One-He Rivers’in West China:The Second Comment on the Concept of‘Hongqi River Project’”argues that the interannual variation of the“Five-Jiang and One-He Rivers”runoff and the specific runoff of each node is much less than the“Hongqi River Project”.Based on the above paper and the data and results available,this paper further elaborates the runoff of these rivers,the distribution of non-uniformity and flood characteristics during a year,and their constraints on inter-basin water transfer.Researches show that the runoff of“Five-Jiang and One-He Rivers”from November to April of the next year only accounts for 12.09%~21.84%of the total annual runoff,and the monthly average is only 2.01%~3.64%.Winter and spring are dry seasons.The runoff of these two seasons is only slightly more than the monthly average of 1.67%or 1.75%of the proposed water transfer ratio of 20%or 21%.Such a small amount of water can only maintain the ecological and domestic water in the basin,and it is obviously impossible to transfer water across river basins.Moreover,it is difficult for the middle and lower reaches of the“Hongqi River”to transfer water during the winter icing period.In the four months from June to September every year,the“Five-Jiang and One-He Rivers”runoff accounts for 53.3%~88.3%of the annual runoff,and even the monthly runoff in August can reach 17.8%~29.6%of the annual total runoff which belongs to the flood season.According to the actual data of runoff,the water supply period during a year is only 6 months for the flood and flat water period or 3 to 4 months for the flood season,which is much shorter than the annual water transfer time envisioned by the“Hongqi River Project”.In the time window from May to October of every year when water can be transferred across river basins,the total annual water transfer of“Five-Jiang and One-He Rivers”is only 153.25×10^8 m^3(20%)or 161.50×10^8 m^3(21%),if the monthly average water flow rate is 1.67%or 1.75%according to the original idea.The amount of water is only one-fourth of the original idea of 60 billion m^3,and it is less than 27%at the best.Achieving an annual runoff ratio of 20%or 21%in the 6 months of the high and normal water periods means that the monthly runoff ratio of 1.67%or 1.75%will increase to 3.33%or 3.50%.In this way,the total annual water transfer of“Five-Jiang and One-He Rivers”can reach 306.50×10^8 m^3 or 323.00×10^8 m^3.This water transfer scheme will double the cross-sectional area of the water transfer channel or the project scale,but the water transfer volume is only about half or at most 54%of the original idea.With a powerful water transfer capacity of nearly 60 billion m^3,the water transfer ratio of the“Five-Jiang and One-He Rivers”will increase to 27.1%of the annual runoff(before the west line of project for diverting water from the south to the north started),or 39.0%of the other water transfer rivers except the Jinsha River and the Yalong River(afer the west line of project for diverting water from the south to the north project completed),and the scale of the“Hongqi River”is bound to increase greatly,which also means that the difficulty of the project is greatly increased,the cost of engineering construction and operation is greatly increased,and the risk of floods,earthquakes and geological disasters is greatly increased.The actual adjustable water volume of“Five-Jiang and One-He Rivers”is significantly reduced compared with the concept of“Hongqi River”,which makes the scientific foundation and scientific basis of the“Red Flag River”project argument questionable.