Spatial-temporal characteristics analysis method of basin water cycle change based on numerical simulation

Abstract

The basin water security is related to food security, people's health, and social stability. To explore the historical evolution law of basin water cycle under the background of global warming and socio-economic development, a set of spatial-temporal characteristic analysis method for basin water cycle changes based on numerical simulation is established, which is of great significance for formulating relevant policies to adapt to and mitigate future possible water disasters. Taking the Chao Phraya River Basin in Thailand as an example, a high-resolution distributed hydrological model GBHM is constructed by comprehensively applying measured meteorological, hydrological and underlying surface data. The hydrological process of the Chao Phraya River Basin from 1985 to 2014 is numerically simulated, the spatial-temporal evolution law of water cycle elements and vegetation is analyzed, and the “double peak” characteristic of annual rainfall distribution is clarified based on the EOF method. The result show that the spatial distribution of precipitation in the Chao Phraya River Basin is uneven, concentrated in the northeast and southeast regions; over the past 30 years, the average annual rainfall in the whole basin and the four sub-basins of the upper reaches, including the Bang River, Wang River, Yong River and Nan River, has shown a significant upward trend, with the increase rates being 1.25 mm/a, 1.06 mm/a, 1.50 mm/a, 2.61 mm/a and 0.65 mm/a respectively; the annual precipitation distribution in the basin shows a double-peak pattern, of which the first peak appearing from March to May is mainly affected by the South Asian monsoon, and the second peak appearing from July to September is mainly affected by the Northwest Pacific monsoon and tropical cyclones; over the past 30 years, the annual runoff of the Chao Phraya River Basin and the four sub-basins in the upper reaches has shown a significant upward trend, with the increase rates being 284 million m³/a, 62 million m³/a, 29 million m³/a, 78 million m³/a and 104 million m³/a respectively. The result indicate that the South Asian monsoon dominates the early rainfall peak in the basin, while the Northwest Pacific monsoon and tropical cyclones dominate the late rainfall peak; the significant enhancement of the South Asian monsoon and tropical cyclones during the rainy season causes an increase in heavy rain, which in turn leads to intensified floods. Through the analysis of the spatial-temporal characteristic changes of various elements in the basin water cycle process, the unique role of the numerical simulation-based spatial-temporal characteristic analysis method in the analysis of basin water cycle elements is fully demonstrated, which can provide analytical tools and useful references for the formulation of basin water security policies.

Keywords

a typical tropical basin in Southeast Asia / water cycle change / a distributed hydrological model / the EOF method