Spatiotemporal dynamics of land and water resources matching of cultivated land use based on micro scale in Naoli River Basin

Abstract: Water and soil are the core of cultivated land use. Their matching in space and time is closely related with sustainable use of cultivated land and grain security. In this study, we analyzed the spatiotemporal dynamics of land and water resources matching of cultivated land use based on micro scale in Naoli River Basin. The crop evapotranspiration was calculated as the index of cultivated land water demand. The available water supply was calculated based on water balance equation in dryland and paddy field. The data of cultivated land use during main growing stages of crops (corn and rice) were derived from Landsat TM/OLI. Meteorological and crop growth data were from local meteorological stations. From the perspective of supply and demand, a land and water resources matching index model was built. The research unit of 30 m by 30 m grid was used to quantitatively analyze spatiotemporal distribution and dynamics of water demand, available water supply and land and water resources matching index of cultivated land in the whole crop growing stage and different crop growing stages from 2000 to 2015, which was based on the comprehensive consideration of factors such as regional climate and water resource change, planting structure adjustment, the difference in available water supply between dry and paddy field, and the difference of water demand of cultivated land in different crop growing stages. The results showed that: 1) Cultivated land in the study area continued to increase. Its area increased by 15.79% from 2000 to 2015. The proportion of paddy field in the total cultivated land increased to 36.28% in 2015 from 22.70% in 2000 and the proportion of dryland in the total cultivated land decreased to 63.72% in 2015 from 77.30% in 2000. The increased paddy field was mainly distributed in the west of the middle reaches and lower reaches of Naoli River Basin. 2) The water demand and available water supply of cultivated land use in the whole crop growing stage and each crop growing stage all showed upward trend, except that water demand fluctuated around 2.92×109 m3 in the early crop growing stage and available water supply decreased in the late crop growing stage. 3) The variation range of land and water resources matching index of cultivated land use increased but mainly distributed below 0.45 in the whole crop growing stage, the degree of land and water resources matching increased and its differentiation enhanced in the study area. The change of land and water resources matching index in each crop growing stage was complex and it showed obvious periodic characteristics taking 2010 as a boundary, land and water resources matching index of cultivated land increased slowly in early and middle crop growing stages while decreased rapidly in late crop growing stage from 2000 to 2010, and the land and water resources matching index of cultivated land use increased rapidly in early and middle crop growing stage while decreased slowly in late crop growing stage from 2010 to 2015. 4) Under the influence of the structure and distrubution of cultivated land use, the spatial dynamic change of water demand, available water supply, land and water resources matching index of cultivated land use in Naoli River Basin were all characteristiced with high values transfering and expanding from the eastern middle reaches to the western middle reaches and the lower reaches. The study will provide valuble information for efficient utility of cultivated land and water resources in Naoli River Basin.