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Abstract: The topography, hydroperiod, water table, and selected edaphic characteristics are described for Piermont Marsh, an irregularly flooded tidal marsh in the Hudson River Estuary, New York, USA. Despite variations in microtopography, overall the marsh is flat, and although the observations were conducted at a high point in the Estuary''s 18.6 year metonic cycle, its surface was only inundated 10–12 times a month. Observations of spatial differences in the saturated hydraulic conductivity and surface infiltration rates are also discussed. ‘Edge’ portions of the marsh are characterized by a slightly higher, more uniform, more structured, less organic, and less hydrologically conductive substrate than found in the marsh interior. Preferential flow is facilitated by macropores in the creekbank wall. The water table is close to the marsh surface for a lesser percentage of the lunar month in the marsh ‘edge’ when compared to the interior, where it is almost always within 10cm of the surface. The extent to which the spatial variability of these hydrologic characteristics determines the marsh''s ability to provide various ecosystem services is also discussed and the implications of these observations on tidal marsh restoration efforts briefly presented. [Copyright &y& Elsevier]

Soil and water conservation structures, promoted by local and international development organizations throughout rural landscapes, aim to increase recharge and prevent degradation of soil surface characteristics. This study investigates this unexamined relationship between recharge, water table depths, and soil surface characteristics (nutrients) in a small sub-watershed in the northwestern Ethiopian highlands. These highland watersheds have high infiltration rates (mean 70 mm hr −1 , median 33 mm hr −1 ), recharging the shallow unconfined hillslope aquifer with water transport occurring via subsurface pathways down the slope. The perched water tables reflect the subsurface flux and are deep where this flux is rapid in the upland areas (138 cm below surface). Soil saturation and overland flow occur when the subsurface flux exceeds the transport capacity of the soil in the lower downslope areas near the ephemeral stream (19 cm below surface). Land use is directly related to the water table depth, corresponding to grazing and fallowed (saturated) land in the downslope areas and cultivated (unsaturated) land in the middle and upper parts where the water table is deeper. Kjeldahl Total Nitrogen (TN), Bray II available phosphorus (AP), and exchangeable potassium (K + ) averages exhibit different behaviors across slope, land use transects, or saturation conditions. TN was moderate to low (0.07% ± 0.04) in various land uses and slope regions. Bray II AP had very low concentrations (0.25 mg kg −1  ± 0.26) among the different slope regions with no significant differences throughout (p > .05). The exchangeable cation (K + , Ca 2+ , Mg 2+ ) concentrations and pH, however, were greater in non-cultivated (seasonally saturated) lands and in a downslope direction (p < .001, p < .005, p < .05, and p < .005, respectively). These results show that the perched groundwater plays an important role in influencing land use, the amount of water seasonally available for crop growth, and exchangeable cations, but have no clear effect on the concentration of the two primarily applied nutrients in fertilizers (N, P). [ABSTRACT FROM AUTHOR]

Because water shortages limit development in many parts of the world, a systematic approach is needed to use water more productively. To address this need, Molden and Sakthivadivel [Water Resour. Dev. 15 (1999) 55-71] developed a water-accounting procedure for analyzing water use patterns and tradeoffs between users. Their procedure treats groundwater and surface water as a single domain. We adapted this procedure to account for groundwater and surface water components separately, and applied the adapted procedure to the Singkarak–Ombilin River basin, Indonesia, where groundwater is a significant part of the overall water balance. Since 1998, a substantial proportion of water has been withdrawn from Singkarak Lake and diverted out of the basin, resulting in significant impacts on downstream water users and the lake ecosystem. Based on 15–20 years (1980–1999) of hydrometeorological, land use, soil, and other relevant data, a simple groundwater balance model was developed to generate the hydrogeologic information needed for the water-accounting procedure. The water-accounting procedure was then used to evaluate present and potential future water use performance in the basin. By considering groundwater and surface water components separately, a more realistic estimate of water availability was calculated than could be obtained by lumping these components together. Results show that the diversion of 37 m3/s from Singkarak Lake increases the amount of water that is not available for other uses, such as for irrigation, from 57–81 to 81–95% of total water available in the basin. The new water accounting procedure also demonstrates the viability of increasing downstream water supply and water use performance during the dry months (June–September). For example, by increasing irrigation during the wet months (January–April) or tapping water from a shallow, unconfined aquifer during the dry months, while keep maintaining sustainable groundwater levels. [Copyright &y& Elsevier]