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In coastal regions of the Netherlands, various aspects of salinity were recognized and dealt with throughout history: causes of salinization and sodification, desalinization, soil structure deterioration and rehabilitation, crop salt tolerance/intolerance, and soil and crop management. Originally, experience of water managers and farmers formed the basis. From 1850 onward, first mainly chemical analysis, later combined with physico-chemical concepts, and still later also analyses of flow and transport processes, and plant physiology were used to transform traditional opinions into scientific understanding. In the 20th century, salinization and sodification arose from natural floods (1906, 1916, 1953) and strategic wartime inundations (1939/1940, 1944/1945), and in the context of creation of the Zuiderzee Works and the Delta Works. J.M. van Bemmelen (1830–1911) pioneered diagnosis of salinity and the study of acid sulfate soils, while D.J. Hissink (1874–1956) understood sodicity and promoted application of gypsum. These early studies were amplified, respectively, by C. Nobel and S. Smeding on monitoring salinity, by A.J. Zuur and B. Verhoeven on desalinization, by W.H. van der Molen and G.H. Bolt on ion exchange, and by K. Zijlstra and C. van den Berg on salinity tolerance/intolerance. In the period 1923–1940, the civil engineer J.P. Mazure studied seepage from saline open water into lower lying land and diffusion and convection of salts into and out of lake bottoms. [ABSTRACT FROM AUTHOR]

Summary: This article describes the post audit and inverse modeling of a 1-D forward reactive transport model. The model simulates the changes in water quality following artificial recharge of pre-treated water from the river Rhine in the Amsterdam Water Supply Dunes using the PHREEQC-2 numerical code. One observation dataset is used for model calibration, and another dataset for validation of model predictions. The total simulation time of the model is 50years, from 1957 to 2007, with recharge composition varying on a monthly basis and the post audit is performed 26years after the former model simulation period. The post audit revealed that the original model could reasonably predict conservative transport and kinetic redox reactions (oxygen and nitrate reduction coupled to the oxidation of soil organic carbon), but showed discrepancies in the simulation of cation exchange. Conceptualizations of the former model were inadequate to accurately simulate water quality changes controlled by cation exchange, especially concerning the breakthrough of potassium and magnesium fronts. Changes in conceptualization and model design, including the addition of five flow paths, to a total of six, and the use of parameter estimation software (PEST), resulted in a better model to measurement fit and system representation. No unique parameter set could be found for the model, primarily due to high parameter correlations, and an assessment of the predictive error was made using a calibration constrained Monte-Carlo method, and evaluated against field observations. The predictive error was found to be low for Na+ and Ca2+, except for greater travel times, while the K+ and Mg2+ error was restricted to the exchange fronts at some of the flow paths. Optimized cation exchange coefficients were relatively high, especially for potassium, but still within the observed range in literature. The exchange coefficient for potassium agrees with strong fixation on illite, a main clay mineral in the area. Optimized CEC values were systematically lower than clay and organic matter contents indicated, possibly reflecting preferential flow of groundwater through the more permeable but less reactive aquifer parts. Whereas the artificial recharge initially acted as an intrusion of relatively saline water triggering Na+ for Ca2+ exchange, further increasing total hardness of the recharged water, the gradual long-term reduction in salinity of the river Rhine since the mid 1970s has shifted to an intrusion of fresher water causing Ca2+ for Na+ exchange. As a result, seasonal and longer term reversal of the initial cation exchange processes was observed adding to the general long-term reduction in total hardness of the recharged Rhine water. [Copyright &y& Elsevier]

Question: How does groundwater input affect plant distribution in Alnus glutinosa (black alder) carrs? Location: Alder carrs along the river Meuse, SE Netherlands. Methods: Three types of site, characterized by groundwater flow, were sampled in 17 A. glutinosa carrs. Vegetation and abiotic data (soil and water chemistry) were collected and analysed using a Canonical Correspondence Analysis. Based on the results, a laboratory experiment tested the effect of groundwater input (Ca2+) on pore water chemistry (NH4+ availability). Results: Environmental factors indicating groundwater input (Ca2+ and Fe2+), correlating with the NH4+ concentration in the pore water, best explained the variation in plant distribution. NH4+ availability was determined by Ca2+ input via the groundwater and subsequent competition for exchange sites in the sediment. As a result, nutrient-poor seepage locations fully fed by groundwater were dominated by small iron resistant plants such as Caltha palustris and Equisetum fluviatile. More nutrient-rich locations, fed by a combination of groundwater and surface water, allowed the growth of taller iron resistant plant species such as Carex paniculata. Nutrient-rich locations with stagnating surface water were hardly fed by groundwater, allowing the occurrence of fast growing and less iron tolerant wetland grasses such as Glyceria fluitans and G. maxima. Conclusion: Groundwater input affects plant composition in A. glutinosa carrs along the river Meuse by determining nutrient availability (ammonium) and concentrations of toxic iron. [ABSTRACT FROM AUTHOR]

Abstract: Soils of wet heathlands have lost their buffering capacity as a result of acidification, eutrophication, and desiccation. Many characteristic plant species have disappeared from these ecosystems because of the unfavourable soil conditions. Restoration projects should aim at counteracting the negative effects of acidification in particular. Blocking of drainage ditches to increase groundwater influence and lime application to improve soil pH and buffering capacity have been applied in many restoration projects in the Netherlands, but with varying success. In this mesocosm experiment, the restoration of the soil buffering capacity of degraded wet heath soil was studied. Groundwater with low or high calcium and bicarbonate concentrations and low or high flow velocities was applied to soil columns filled with wet heath soil. Measurements of the nutrient concentrations in soil pore water and soil extractions revealed that restoration of the soil buffering capacity was optimal at both high calcium concentrations and high through-flow velocity. It was concluded that high concentrations of calcium are more effective than high flow velocity in the reloading of the buffer capacity. Furthermore, the restoration was limited to the soil layers that were in direct contact with the groundwater, which stresses the need for higher groundwater levels in degraded wet heathlands. [Copyright &y& Elsevier]