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Vulnerability of wetland vegetation to water table changes is a widely studied topic in the field of ecology. Extreme flood or drought conditions imposed on wetlands cause disappearance of plants or shift in the vegetation regime. The recovery of such plant compositions is of particular importance when the wetland is subjected to frequent water table fluctuations resulting from land use changes and requires knowledge of mechanisms underlying evolution of plant growth to changing hydrologic conditions. We used a spatially varying, coupled groundwater–vegetation growth model to investigate the survival mechanism of wetland herbaceous plants. The plants were subjected to long‐term water table drainage because of land use changes that caused the disappearance of one of the species composition. In an effort to revive the disappeared species, hypothetical soil saturation was introduced onto the study domain through elevated water table level. Even though the system had returned to hydrologically favourable environment, the disappeared species was unable to recover, which in turn led to the evaluation of factors that determine the re‐emergence of the species through sensitivity analysis. The results of the sensitivity analysis showed that the disappeared species recovered during scenarios of reduced duration of drawdown, increased assimilation rates and increased competitiveness. The analysis also showed that the competitiveness of the plants, which was modelled by the classic Lotka–Volterra algorithm, supersedes any of the unfavourable plant growth characteristics. The results of this study demonstrated the ability of the groundwater–vegetation response model to facilitate an understanding of plant development and a hierarchy of important factors that promote their growth in altered hydrologic conditions. Copyright © 2012 John Wiley & Sons, Ltd.

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Streamflow measurements provide information about the flow generation characteristics of land surfaces as well as the flow transferring nature of the channel network. In this study, such flow transferring properties of the channel network that were obtained from downstream flow observations were used for predicting flow in ungauged basins. A temporally averaged transfer function (ATF) of the channel segments of Kentucky River Basin (KRB) in Kentucky, USA, was extracted from observed hydrographs in a time‐invariant system as a function of drainage area. The ATF was regionalized through multiple regression analysis for 194 combinations of drainage areas that differ in topography, terrain, and geology. The application of ATF for flow prediction in ungauged basins was performed for Goose Creek, a subbasin of KRB by integrating ATF with the TOPMODEL. In addition, the ATF was shown to be capable of providing calibration and validation data for ungauged basins in a backward technique from a measured stream gauge downstream, with minimal data requirement of drainage area. The applicability of ATF was illustrated across a range of streamflow conditions from watersheds that varied greatly in their terrain and geology. Nash–Sutcliffe efficiency of the proposed method, as a function of drainage areas of the corresponding basins, to predict daily streamflow from ungauged basins ranged from 0.83 to 0.92. The results of the study concluded that the ATF obtained from measured streamflow thus proved to be a quick and simple tool for assessment of streamflow in both operational and modeling hydrology. Copyright © 2012 John Wiley & Sons, Ltd.

Departures in precipitation from the normal are the cause of the onset of agricultural drought. In this study, we aim to identify extreme precipitation deficits using an index called Percent Normal (PN). We applied the proposed PN index to the agriculturally productive Mekong River Basin (MRB) to evaluate the propagation of precipitation deficits into agricultural drought based on the change in slope and mean of the precipitation, soil moisture and evapotranspiration anomalies. The results of the study showed the proposed PN index identified historical droughts in the years 1992, 1997–1998 and 2000–2006 in MRB; of these, 1992 was shown to be the longest drought, which lasted from the 43rd week (October) of 1991 to the 49th week (December) of 1994. The short-term but extreme drought was identified to occur in 2005 with below-normal precipitation that lasted for more than a year. An immediate effect of precipitation deficit was observed in evapotranspiration (ET) and soil water for agricultural (Thailand) and forested regions (Parts of Cambodia) of the basin with <5 weeks lag. We conclude that the drought indices adopted in this study are suitable to identify the small and long-term drought events, which will facilitate the development of a drought-resilient agricultural production system.