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Guo H.P.,China Institute of Geo Environmental Monitoring
Advanced Materials Research | Year: 2014

This paper reviews the analytical solutions for the impact of land reclamation on the ground water level and the saltwater interface with unconfined groundwater conditions in coastal aquifers. The applicability of the analytical solutions is somewhat limited by assumptions such as Dupuit-type flow and the Ghyben-Herzberg relation. Variable-density flow and solute transport simulations conducted by the numerical code FEFLOW were used to evaluate the accuracy of these analytical solutions. Three field-scale hypothetical cases were simulated for the numerical verification. The results show that a seepage face occurs in the numerical results rather than in the analytical solutions, but only minor difference occurs between the numerical and analytical solutions. This implies that the analytical solutions are reasonable despite the used assumptions. © (2014) Trans Tech Publications, Switzerland. Source

Cao G.,Water Resources University | Cao G.,University of Alabama | Zheng C.,University of Alabama | Zheng C.,Peking University | And 3 more authors.
Water Resources Research | Year: 2013

The North China Plain (NCP) is one of the global hotspots of groundwater depletion. Currently, our understanding is limited on spatiotemporal variability in depletion and approaches toward more sustainable groundwater development in this region. This study was intended to simulate spatiotemporal variability in groundwater depletion across the entire NCP and explore approaches to reduce future depletion. Simulated predevelopment groundwater recharge (∼ 13 km yr) primarily discharged as base ow to rivers and evapotranspiration. Initial groundwater storage was estimated to be 1500 km of drainable storage in shallow aquifers and 40 km of compressive storage in deep aquifers. Simulated groundwater depletion from 1960s to 2008 averaged ∼4 km /yr. Cumulative depletion was 50 km (∼20% of pumpage) in the piedmont district, 103 km (∼20%) in the central plain, and 5 km (12%) in the coastal plain. However, depletion varied with time : ∼2.5 km /yr in the 1970s, ∼4.0 in the 1980s, ∼2.0 in 1990-1996; ∼7.0 in 1997-2001, and ∼4.0 in 2002-2008. Recharge also varied spatially, averaging ∼120 mm/yr and concentrated in the piedmont district (200-350 mm/yr) while lower in the central and coastal plains (50-100 mm/yr). Simulation of several alternatives, including managed aquifer recharge, increased water use efficiency, brackish water use, and interbasin water transfer, indicated that the combination of these strategies could be used to recover groundwater storage by 50 km over a 15-year period. This study provides valuable insights for developing more sustainable groundwater management options for the NCP ; the methods are useful for managing other depleted aquifers. © 2013. American Geophysical Union. All Rights Reserved. Source

Guo H.,China Institute of Geo Environmental Monitoring | Guo H.,University of Hong Kong | Jiao J.J.,University of Hong Kong | Li H.,Wuhan University
Journal of Hydrology | Year: 2010

A coastal aquifer may consist of two zones of distinctly different hydraulic properties, with the coastal zone of limited width and the inland zone of infinite width. The analytical solutions for groundwater level response to tidal fluctuation in such a two-zone aquifer are derived and the underlying physical meanings are discussed. A dimensionless zone-contrast parameter r is introduced, which is controlled by ratio between the product of the transmissivity and storativity of the inland zone and that of the coastal zone. In the coastal zone, the amplitude of groundwater head fluctuation attenuates more quickly when r becomes greater. The amplitude declines exponentially with distance from the coastline, and the phase lag increases linearly only when r = 1. In the inland zone, however, the head fluctuation always exhibits an exponential attenuation of the amplitude and a linear increase of the phase lag for any value of r. Thus, the diffusivity of the inland zone can be readily assessed with measurements of fluctuation amplitudes or lags, as are frequently used when estimating aquifer parameters in homogeneous aquifers. Compared with Jacob (1950) solution for a semi-infinite homogeneous aquifer, the existence of the coastal zone reduces the amplitude in the inland zone by a spatially constant coefficient and increases the phase lag by a spatially constant shift. Inverse estimation of aquifer parameters are discussed based on the analytical solutions. The analytical solutions are used to estimate the aquifer parameters in a coastal two-zone aquifer located in the west part of Dongzhai Harbor, Hainan Province, China. © 2009 Elsevier B.V. All rights reserved. Source

Xu C.,China Earthquake Administration | Xu C.,CAS Institute of Geology and Geophysics | Xu X.,China Earthquake Administration | Dai F.,CAS Institute of Geology and Geophysics | And 5 more authors.
Natural Hazards | Year: 2013

The main purpose of this paper is to present the use of multi-resource remote sensing data, an incomplete landslide inventory, GIS technique and logistic regression model for landslide susceptibility mapping related to the May 12, 2008 Wenchuan earthquake of China. Landslide location polygons were delineated from visual interpretation of aerial photographs, satellite images in high resolutions, and verified by selecting field investigations. Eight factors, including slope angle, slope aspect, elevation, distance from drainages, distance from roads, distance from main faults, seismic intensity and lithology were selected as controlling factors for earthquake-triggered landslide susceptibility mapping. Qualitative susceptibility analyses were carried out using the map overlaying techniques in GIS platform. The validation result showed a success rate of 82.751 % between the susceptibility probability index map and the location of the initial landslide inventory. The predictive rate of 86.930 % was obtained by comparing the additional landslide polygons and the landslide susceptibility probability index map. Both the success rate and the predictive rate show sufficient agreement between the landslide susceptibility map and the existing landslide data, and good predictive power for spatial prediction of the earthquake-triggered landslides. © 2013 Springer Science+Business Media Dordrecht. Source

Li Y.,CAS Research Center for Eco Environmental Sciences | Luo Y.,China Institute of Geo Environmental Monitoring | Liu G.,CAS Research Center for Eco Environmental Sciences | Ouyang Z.,CAS Research Center for Eco Environmental Sciences | Zheng H.,CAS Research Center for Eco Environmental Sciences
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

Ecosystem services are the goods and services provided by ecosystems to people. Ecosystem services are important basis of human existence and strongly related to human well-being, and the sustainable provision of multiple services is essential for the sustenance of human societies. There are a series of factors driving ecosystem services, one of which is the change of land use pattern, and it is drawing more and more attention of ecologists. Miyun reservoir, which is the only surface water source for domestic water in Beijing, plays the key role for the ecological security of the capital. Miyun reservoir watershed is a vital water source region of Beijing city, and it has many important ecosystem services. The water yield and water quality of reservoir strongly depend on Miyun reservoir watershed's condition, therefore, the conservation and improvement of ecosystem services in Miyun reservoir watershed has vital significance for local and Beijing's ecological security. However, how the land use change influenced ecosystem services during the past decades is not clear yet, which may block the comprehensive development of watershed. So we take Miyun reservoir watershed as example, analyze the change of land use and ecosystem services between 1990 and 2009. We set up a two-grade classify system of land use and interpreted the remote sensing images of 1990, 2000 and 2009 respectively, and then apply Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST model), which is a space explicit model and based on land use, to map the ecosystem services, and analyze the influence of Land Use to ecosystem services during study period. The sub models we apply in this research contain "Water Yield", "Sediment Retention"and "Water Purification", and before running these sub models, we verify them with observed data. The results of image interpretation show that farmland, forest and grassland are main type of land use of watershed, and these areas account for more than 95% of the whole watershed. There are sharp changes of land use during study period, and conversion of land use types distributed more widely after 2000. The general trend in study period is farmland and grassland decreased by 30%, 48% respectively, when forest increased by 30%, and another change cannot be neglected is residential area expanded by more than 280% during the past 20 years. The changes of land use have affect on the pattern of ecosystem services and there are trade-offs among different ecosystem services in question. During the study period, the decreasing of farmland and increasing of forest and grassland improved the ability of sediment retention, and this service increased by 46% in the past 20 years. But forest expansion caused more evapotranspiration, which reduced water yield of watershed by 3% at the same time. Because the nutrient loading of residential area is much higher than other types of land use, the large-scale expansion of residential area decreased water purification service sharply after 2000 although the expansion of forest and decrease of farmland can improve this service to a certain degree, and this service declined by 55% in the past 20 years. With the expansion of forest, carbon sequestration service increased about 19%. So with the goal to get overall improvement of ecosystem services in watershed, we suggest that manages should strengthen the control of forest and residential areas. Understanding the relationship between land use and ecosystem services, the department of decision-making can control and reduce the trade-off between ecosystem services and achieve the sustainable development through appropriate land use plan. Although the approach and process of evaluation still need more improvement, our research can provide scientific foundation for decision-making in Miyun reservoir watershed. Source

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