Soil saturation index of salt marshes subjected to spring‐neap tides: a new variable for describing marsh soil aeration condition

Organized spatial distribution of plants (plant zonation) in salt marshes has been linked to the soil aeration condition in the rhizosphere through simplistic tidal inundation parameters. Here, a soil saturation index (ratio of saturation period to tidal period at a soil depth) is introduced to describe the soil aeration condition. This new index captures the effects of not only the tidal inundation period and frequency but also the flow dynamics of groundwater in the marsh soil. One‐dimensional numerical models based on saturated flow with the Boussinesq approximations and a two‐dimensional variably saturated flow model were developed to explore the behaviour of this new soil aeration variable under the influence of spring‐neap tides. Simulations revealed two characteristic zones of soil aeration across the salt marsh: a relatively well aerated near‐creek zone and a poorly aerated interior zone. In the near‐creek zone, soils undergo periodic wetting and drying as the groundwater table fluctuates throughout the spring‐neap cycle. In the interior, the soil remains largely water saturated except for neap tide periods when limited drainage occurs. Although such a change of soil aeration condition has been observed in previous numerical simulations, the soil saturation index provides a clear delineation of the zones that are separated by an ‘inflexion point’ on the averaged index curve. The results show how the saturation index represents the effects of soil properties, tidal parameters and marsh platform elevation on marsh soil aeration. Simulations of these combined effects have not been possible with traditional tidal inundation parameters. The saturation index can be easily derived using relatively simple models based on five non‐dimensional variables. Copyright © 2010 John Wiley & Sons, Ltd.     

An approach to catchment‐scale groundwater nitrate risk assessment from diffuse agricultural sources: a case study in the Upper Bann,Northern Ireland

DRASTIC has drawbacks in groundwater risk assessment that are important in guiding activities to prevention agricultural diffuse groundwater pollution. This paper presents an improved and GIS‐based D‐DRASTIC approach for groundwater nitrate risk assessment from diffuse agricultural sources based on DRASTIC. D‐DRASTIC considers the risk concept, nitrate loading, pollutant transport with runoff, depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and the hydraulic conductivity of the aquifer. D‐DRASTIC was developed within an ArcGIS environment and applied to the Upper Bann Catchment, Northern Ireland as a case study. D‐DRASTIC shows that ‘very high’ and ‘high’ zones of groundwater nitrate risk occupy 5% and 11% of the case study area, respectively. When considering groundwater pollution sources and pathways, the results using D‐DRASTIC are helpful in guiding the activities of groundwater pollution prevention at the catchment scale in the context of better implementation of the EU Water Framework Directive. Copyright © 2008 John Wiley & Sons, Ltd.     

深层地下水SPD人工补给系统

提出了一种新的深层地下水回灌方法———SPD人工补给系统,并通过室内沙槽模拟试验,对该系统和常规的直接井回灌法作了比较。研究表明,利用该系统补给深层地下水,具有回灌水质要求低、补给速度快、补给量多、不易淤堵等特点,是深层地下水人工补给的一条有效的新途径。     

Influence of a hedge surrounding bottomland on seasonal soil‐water movement

The influence of a hedge surrounding bottomland on soil‐water movement along the hillslope was studied on a plot scale for 28 months. The study was based on the comparison of two transects, one with a hedge, the other without, using mainly a dense grid of tensiometers. The influence of the bottomland hedge was located in the area where tree roots were developed, several metres upslope from the hedge, and could be observed both in the saturated and non‐saturated zone, from May to December. The hedge induced a high rate of soil drying, because of the high evaporative capacity of the trees. We evaluated that water uptake by the hedge during the growing season was at least 100 mm higher than without a hedge. This increased drying rate led to a delayed rewetting of the soils upslope from the hedge in autumn, of about 1 month compared with the situation without a hedge. Several consequences of this delayed rewetting are expected: a delay in the return of subsurface transfer from the hillslope to the riparian zone, a buffering effect of hedges on floods, already observed at the catchment scale, and an increased residence time of pollutants. Copyright © 2003 John Wiley & Sons, Ltd.     

The spatial distribution of groundwater flooding in a chalk catchment in southern England

Groundwater flooding occurred in the upper parts of many chalk rivers in the UK during the exceptionally wet winter of 2000–01. This provided a rare opportunity to investigate the spatial distribution of groundwater discharge and flooding along the normally dry intermittent headwaters of a chalk catchment. The extent of flooding along the River Pang, upstream of the seasonal head, was mapped using aerial photography, and point measurements of flow and water temperature were used to identify the contributing reaches of the river. The results are discussed in the context of the geological and groundwater conditions. The occurrence of flooding can largely be explained by the regional groundwater flow directions, but increased flow in some locations may be as a result of preferential groundwater flow along lines of geological structure. Published by John Wiley & Sons, Ltd.     

论提高环境水文地质图件制图工艺

近年来，地图制图理论有了较快的发展，如何将信息传输和视觉感受等方面的研究成果运用于环境水文地质图的编制，是制图工作者和专业人员共同关注的一个重要问题。本文以编制城市环境水文地质图为例，就制图过程中的一些原则和方法作一探讨。     

矿山废石淋溶对水环境的影响

为了研究废石堆砌对水环境的影响,通过对废石做淋溶实验,分析了出入水的水质变化规律,对废石衍生环境效应的过程、机制、影响因素方面进行讨论,揭示了人们容易忽视的酸性水中硫酸根、总硬度、微量金属离子的动力学变化机理,指出矿山废石对水环境的污染不至限于使水质酸化,硫酸根、总硬度也会大幅度提高,废石堆放应充分考虑当地的地理气候及水文条件,合理堆放,减少污染。     

洛阳市供水前景预测及对策探讨

洛阳市地下水资源量丰质优，远期供水前景较为乐观。然而，由地下水开采引起的环境水文地质问题仍属客观存在。本文在供水前景预测的基础上，提出了五项对策，对城市远期供水规划具借鉴意义。     

Simulation of groundwater dynamics in the North China Plain by coupled hydrology and agricultural models

We simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment‐based Ecohydrology (NICE) model with DSSAT‐wheat and DSSAT‐maize, two agricultural models. This combined model (NICE‐AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE‐AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE‐AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd.