| With the global warming, the frequency of extreme weather events such as drought and flood has increased. In the latest decade, severe drought occurred almost every year. Haihe basin is one the places where drought happens most frequently of China. Drought in Haihe basin affects widely and has long duration. There is an old saying that nine years out of ten will see drought in Haihe basin. As our country’s important major grain producing area with high socio-economy development level, socio-economy and ecological environment of Haihe basin have suffered a lot due to drought. This paper focused on the temporal and spatial evolution law of drought in Haihe basin and used proxy data (tree-rings), observed data (meteorological and hydrological data) and historical data to evaluate drought of Haihe basin. Temporal and spatial evolution law of drought was analyzed. Combined with existing climate change prediction data, the future development trend of drought in the study area was predicted and macro strategy against drought in the future was carried out. The main conclusions were as follows:(1) Analysis of temporal evolution law of drought in mountain area of Haihe basin.Combined with proxy data, observed data, the temporal evolution law of mountain area of Haihe basin was analyzed. The results showed that tree-ring residual chronology of Chinese pine of Xiaowutai Mountain—which was chosen as the typical area—has obvious correlation with spring precipitation and spring severe droughts of the study area. Besides, tree-ring width ranges from0to0.80could indicate severe spring drought years of the study area. In order to increase accuracy rate of the results, meteorological and hydrological data were used to do mutual verification. Using meteorological data, evolution law of indexes such as precipitation, potential evaporation, relative humidity degree were analyzed. The results showed that the intensity of spring drought has slightly decreased while annual drought intensity has an increasing trend. Hydrological data was used to analyze the runoff anomaly rate of six typical hydrological stations of the study area, showing a decreasing trend.(2) Analysis of spatial evolution law of drought in mountain area of Haihe basin.In the recent200years, the intensity of the heavy drought years has increased much. The periodicity of the heavy drought years is shorter than that of mild drought years. The area rate of mild drought and heavy drought increased significantly after the discontinuity point and the area rate of heavy drought years increased much more than the mild drought years with more than85%. The periodicity of Tuhaimajiahe river and the rivers on its south, Luanhe river and the rivers on its north have the same changing trend with that of the whole Haihe river basin. The periodicity of heavy drought in Luanhe river and the rivers on its north is shorter than that of Haihe river basin and Tuhaimajiahe river and the rivers on its south. Mild drought and heavy drought area rate have both increased significantly after the discontinuity point in both Luanhe river and the rivers on its north and Tuhaimajiahe river and the rivers on its south, which has the same changing trend with the whole Haihe river basin. On the whole, Haihe river basin is facing a sever future against drought. The relative humidity degree was used to analyze the evolution law of drought area of Haihe river basin in the recent50years. The results showed that in the recent50years the spring drought area of mountain area in Haihe river basin has a slight decreasing trend while that of the whole basin still has an increasing trend. Tree-ring data and relative humidity degree of mountain area of Haihe basin can be mutually verified and accuracy rate of tree-ring indicating drought years could be increased after introducing relative humidity degree.(3)Using the technology of Nuclear Magnetic Resonance, a kind of Nondestructive Tree-ring Rapid Detection and Analysis System was designed. This sampling system could achieve information such as tree-ring width, tree-ring area and density immediately with no harm to the trees. It has avoided the problem that cores can be easily broke when sampling in the traditional way. Each unit of the system could be disassembled or assembled easily and is suitable for field work. A section of fresh truck was tested in medical magnetic resonance imager. Clear images of tree-ring could be exported. The data of tree-ring width and its curve could also been achieved immediately. The initial test has proved that this system is feasible.(4)Eight Ocean-atmospheric model systems were used to assess the precipitation and temperature of Haihe river basin. Future climate changing trends of Haihe river basin under three different scenarios which are A2(high emission), A1B (medium emission) and B1(low emission) were simulated respectively. The precipitation of the base year,2030and2050has an increasing trend. The northeast and south area will receive more precipitation than the northwest area. The temperature will also has an increasing trend and the northeast and south area will be warmer that the northwest area. The precipitation and temperature of A2scenario (high emission) have the largest increasing degree and that of B1scenario (low emission) have the smallest.Aiming at the drought characteristics such as severe overall situation, spatial differentiation, increasing drought area and shorter periodicity, coping strategies were carried out. |
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