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WETLAND AND WATER RESOURCE MODELING AND ASSESSMENT: A Watershed Perspective - Chapter 6

6 Study on the Intra-Annual Distribution Characteristics of the Water Budget in the Hilly Region of Red Soil in Northeast Jiangxi Province, China Junfeng Dai, Jiazhou Chen, Yuanlai Cui, and Yuanqiu He 6.1 INTRODUCTION In northeast Jiangxi Province, water balance is important for water resource utilization and agricultural regionalization. In this region, the red soil is affected by the subtropical monsoon climate in which rainfall is abundant, but unevenly distributed (Chen and Zhang 2002). The high intensity of rainfall leads to water loss during the rainy season. In addition, the time difference between the distribution of the rainfall and its evaporation causes seasonal drought | 6 Study on the Intra-Annual Distribution Characteristics of the Water Budget in the Hilly Region of Red Soil in Northeast Jiangxi Province China Junfeng Dai Jiazhou Chen Yuanlai Cui and Yuanqiu He 6.1 INTRODUCTION In northeast Jiangxi Province water balance is important for water resource utilization and agricultural regionalization. In this region the red soil is affected by the subtropical monsoon climate in which rainfall is abundant but unevenly distributed Chen and Zhang 2002 . The high intensity of rainfall leads to water loss during the rainy season. In addition the time difference between the distribution of the rainfall and its evaporation causes seasonal drought. Studying the characteristics of the intra-annual distribution of the water budget can help discover the occurrence rules of seasonal drought in the region and assist in adopting measures to increase water use efficiency Huang et al. 2004 . Existing literature has examined aspects of the water problem in red soil areas. Yao 1996 described the water problem including seasonal drought and water storage capacity in a red soil area. Wang et al. 1996 analyzed the variations in rainfall evaporation and water storage and supply in low hilly red soil areas. Xie et al. 2000 studied the status of water resources in 1 000-m2 area using the runoff plot neutron probe and tensiometer. However the water budget in the hilly region of red soil has rarely been investigated systematically. It is difficult to obtain or measure percolation evapotranspiration and runoff accurately in the large- to medium-scale basin and even in the small-scale watershed. Therefore water budget in a scale larger than a field is not easily studied using traditional methods. Model simulation is a viable option for calculating the output of the water budget at a variety of scales. However such studies 59 2008 by Taylor Francis Group LLC 60 Wetland and Water Resource Modeling and Assessment have rarely been undertaken in the red soil areas