近50年黄河入海径流变化特征及影响因素分析*

以黄河口利津站实测、天然径流资料为依据,采用回归分析、相关分析和随机水文学的方法,对黄河入海径流的变化特征进行了分析,并结合流域气候和人类活动资料,定量探讨了近50多年来自然变化和人类活动对入海径流的影响。采用费希尔最优分割法检测出黄河实测入海径流出现1968年、1985年和1996年3个跳跃点,依据3个跳跃点,将入海径流分为4个阶段:即Ⅰ(1950~1968年)和Ⅱ(1969~1985年),Ⅲ(1986~1996年)和Ⅳ(1997~2004年),4个阶段径流量逐阶段递减。根据降雨与径流的相关分析计算出各阶段取水量占入海天然径流量的比重,第Ⅰ阶段为24 ％ ,Ⅱ,Ⅲ和Ⅳ阶段分别升至44 ％ , 65 ％ 和79 ％ ,说明流域取水量的增加是造成入海径流量逐阶段减少和断流严重性增强的主要原因,也反映了黄河入海径流由第Ⅰ阶段受自然变化影响为主逐渐过渡至第Ⅲ阶段后受人类活动影响为主。1985年以后流域暖干化、大水库的调节和水土保持等则是促使径流量减少和断流的辅助因素。

EVOLUTIONARY CHARACTERISTICS OF RUNOFF INTO THE SEA OF THE HUANGHE RIVER AND THEIR CAUSES IN RECENT 50 YEARS

Based on the observed (1950~2005)and natural (1952~2004) runoff data from the Lijin hydrographic station at the Huanghe River estuary, an analysis is made on the evolutionary characteristics of runoff into the sea in the past 50 years using regression, correlation and stochastic hydrology methods. Combining annual mean precipitation, annual mean temperature, and annual water diversion and consumption data collected from the Huanghe River basin, we also discussed the influence of climate change and human activities on the runoff. The Fisher optimize method recognized three possible hopping points (1968,1985 and 1996) in the observed runoff data series, and the rank sum test and the mean value test results show that those three hopping points are dintinct. Using those three hopping points, we divided the runoff into the sea into four phases, including Ⅰ(1950~1968),Ⅱ(1969~1985),Ⅲ(1986~1996),and Ⅳ(1997~2004). The runoff step by step shows a clear decreasing. Effects of climate change on natural runoff in the Huanghe River are studied in the four phases. First we have fitted the relationship between runoff and precipitation／temperature. We found out that the exponential and the linear functions were both feasible because the correlation coefficients were nearly the same using the two functions. Then based on the simulation results of reference 16 using the monthly hydrological model, we interpolated the precipitation and temperature data using linear function. Finally we combined the influence of precipitation (decreasing) and temperature (increasing) together. An approximate estimation of the changes of runoff of the four phases are 5.8 ％ ~10.6 ％ (Ⅰ), 0.8 ％ ~1.5 ％ (Ⅱ), -8 ％ ~-13.4 ％ (Ⅲ), and -10.2 ％ ~-17.8 ％ (Ⅳ). Based on the relationship between the observed and natural runoff, the ratios of water diversion and consumption to natural runoff of four phases are figured out, i.e. , 24 ％ (Ⅰ), 44 ％ (Ⅱ), 65 ％ (Ⅲ), and 79 ％ (Ⅳ). This illuminates that water diversion and consumption is the main cause of runoff decreasing and dry-up severity strengthening. It also confirmed that the runoff changes from Phase I was mainly influenced by natural reasons. After Phase Ⅲ, however, the mainforce became human activities. In this changing process, notable warmer and drier climatic events in the Huanghe River basin, the construction of large reservoirs in the upper and lower basins, as well as water and soil preservation play assistant roles. The probability and the annual channel length of dry-up both have good relationship with runoff into the sea. They are both linearly increasing while runoff decreases before the Xiaolangdi Reservoir was used. After 1999 human activities have been strengthened, although the runoff was still small and the dry-up never happened till today.