2003~2009年鄱阳湖流域土壤水分时空变化特征及影响因素

鄱阳湖流域水文过程是区域研究的热点问题，但相对于其它水文要素而言，土壤水分的时空分布特征及其影响因素尚缺乏系统研究，成为流域水文过程研究不确定性的主要来源之一。采用AMSR E土壤水分数据，从流域、子流域及地表覆被等不同的空间尺度，阐明了鄱阳湖流域2003～2009年土壤水分的年际与年内变化特征，并分析其影响因素。研究表明：在流域尺度上，土壤水分总体呈现中心低、周边高的“漏斗式”空间分布形态，但夏、秋季节空间差异性减弱，年际土壤水分呈现较强的下降趋势，其中以湖区下降速度最大；在地表覆被尺度上，林地土壤水分最高、年际下降速度最低，表明其在年际尺度上对干旱具有较强的调节作用，不同地表覆被类型的土壤水分年内差异较明显，但在6、7及10月差异较小，地表覆被对土壤水分的调节作用减弱；在影响因素方面，降水是土壤水分的主要影响因素，气温、灌溉等则一定程度上影响了土壤水分的变化特征。研究结果不仅有利于加强对流域水文过程的理解与认识，同时可为水资源管理及防旱抗旱等提供科学的辅助依据

SPATIAL AND TEMPORAL VARIATION OF SOIL MOISTURE AND ITS CONTROLLING FACTORS OVER THE POYANG LAKE BASIN FROM2003 TO 2009

The hydrological process of the Poyang Lake Basin is a local hot topic. Soil moisture is an important state variable of the hydrological process and plays a critical role in water balance at basin scale. However, the spatial and temporal variation of soil moisture is still lack of systematic research when compared with others hydrological factors, which leads to a strong uncertainty for the research of the hydrological process. The main objectives of this paper are to illustrate the soil moisture dynamics and its influencing factors at different spatial and temporal scales of the Poyang Lake Basin. For these objectives, this paper firstly obtained the AMSR E soil moisture data set from the National Snow & Ice Data Center (NSIDC, http://nsidc.org/data/amsre/index.html) from 2003 to 2009. Then the soil moisture was downscaled to resolution of 1 km and calibrated through the time series in situ soil moisture. After that, this paper investigated the annual and monthly variations of soil moisture at the spatial scales of basin, sub basin and land cover. Finally, it analyzed the relationships between soil moisture with precipitation, air temperature and land cover to capture the controlling factors. The results show that: i) at the scale of basin, the soil moisture presenteda spatial pattern of “Funnel” with the low soil moisture in center and high around at the basin scale, whereas the spatial difference at summer and fall season wasminor. Temporally, annual soil moisture decreased significantly at both basin and sub basin scale, and the rapidest decrease rate occurredin the Lake area (-035%/year). It implies that it is vulnerable to suffer from drought at the Lake area. Furthermore, there were significant differences among the monthly soil moisture, with the variability about 3~4%. The highest soil moisture mainly occurredin April, while the lowest occurred in September or October. ii) At the scale of land cover, forest obtainedthe highest soil moisture. Annual soil moisture decreased in all land cover types, with the lowest decrease rate occurred in forest area. It implies a strong ability to control drought at annual scale. Monthly soil moisture variedwith the land cover types, but the differences were minor in June, July and October. It demonstrates that the effect of land cover was weakened under the extreme climate condition (i.e., the extreme high precipitation and air temperature). iii) With regards to the controlling factors, soil moisture was positively correlated to precipitation and negatively to air temperature. However, soil moisture was positively correlated to air temperature in the Lake area, which is mainly attributed to the irrigation in summer. Furthermore, the correlation of precipitation was higher than that of air temperature. It means that precipitation plays more important role on the soil moisture. Results of this paper would help to understand the hydrological process, but also support the water resource and drought controlling for the basin