Abstract
China is the largest country in terms of population and its booming urbanization has exerted negative effects on ground-surface hydrological processes at different spatial scales, land-use types, and water balance, such as surface runoff, groundwater recharge, and evapotranspiration. However, it is not yet well understood as to how the modifications of the spatial patterns of landscapes affect the water balance on a regional scale. In this study, the water and energy transfer among soil, plants, and atmosphere (WetSpass) model was applied to evaluate the urbanization effects on the water balance on a regional scale by using Beijing as the case city for this current study. The relationships among impervious surfaces, landscape pattern indices, and water balance components were also quantified. Results indicated built-up land in 2012 was 673 km2 larger than it in 2000, mostly converted from croplands. WetSpass model also indicated the variation rates of annual average surface runoff, evapotranspiration and groundwater recharge were 7%, 0.4% and −2% in the whole Beijing area, while they reached 52%, 6% and −24% in the urban area of Beijing from 2000 to 2012, respectively. At a city scale, four districts—Dongcheng, Xicheng, Chaoyang, and Haidian—were characterized by higher impervious percentage, as reflected by lower groundwater recharge and higher surface runoff than other districts. At quadrat scale, however, groundwater recharge (surface runoff) was negatively (positively) correlated with impervious percentages. For landscape indices, the Aggregation Index was positively correlated with surface runoff and negatively correlated with groundwater recharge while Patch Density Index, Splitting Index, Patch Richness Density Index, and Shannon’s Diversity Index presented opposite relationships. The results of this study can help to develop human knowledge about the impacts of urbanization on hydrological cycles on a regional scale.
Highlights
Due to rapidly increasing population and developing economy, the urban area is expanding rapidly
Our results indicate that the correlation coefficient increased over time, which implied implied that the increased impervious percentages would play a more important role in water distribution due to urbanization in Beijing
In In this paper, wewe mainly studied thethe effects ofof urbanization onon water balance components and this paper, mainly studied effects urbanization water balance components and thethe correlations among water balance components, landscape index, and impervious percentages
Summary
Due to rapidly increasing population and developing economy, the urban area is expanding rapidly. The characteristics of urban hydrological cycle are being increasingly modified. The amounts, rates, locations and timing of water balance components, such as surface runoff, groundwater recharge and evapotranspiration, are making different responses worldwide [1]. In the process of urban expansion, the most important change is the increase of impervious surface, which will affect the groundwater level, interception, evaporation and influence runoff, evapotranspiration and basic flow. Groundwater recharge is vital for water supply of food production, agricultural irrigation and drinking water for most urban areas. Its sources and flow paths can be altered compared with the
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