Exchange between a river and groundwater, assessed with hydrochemical data

We describe the chemical composition of groundwater from an alluvial granular aquifer in a valley fill flood plain (River Thur Valley). The river flows along this valley and is mostly downwelling on its way, indirectly through an unsaturated zone in the upstream part, and directly through the water-saturated bed in the downstream part. River Thur has been channelized with barriers for more than a century. In 1992, the authorities started to restore a section of River Thur with riverbed enlargements. The land use in the flood plain and the seasonal and climatic conditions (e.g., hot dry summer 2003) result in alterations of the natural geochemical composition of the river water. This groundwater is partly to mainly recharged by bank filtration. Several wells exist near the river that draw groundwater for drinking. In some of these wells, the groundwater has a very short residence time in the subsurface of days to weeks. Bed enlargements and other operations for an enhancement of the exchange of water between the river and groundwater increase the contamination risk of the nearby wells. During bank filtration, the groundwater changes gradually its composition, with increasing distance from the river and with depth in the aquifer. From today's changes of the water quality during riverbank filtration, we tried to extrapolate to the groundwater quality that may arise from future river restorations. Today the groundwater body consists of a mixture of groundwater from the seepage of precipitation and from riverbank filtration. The main difference between river water and groundwater results from the microbial activity in riverbed and bank materials. This activity leads to a consumption of O<sub>2</sub> and to a higher partial pressure of CO<sub>2</sub> in the groundwater. Criteria for the distinction of different groundwater compositions are the distance of a well from the river and the subsurface residence time of the groundwater to reach this well

Setting the Standard for Farmland Preservation: Do Preservation Criteria Motivate Citizen Support for Farmland Preservation?

The multifunctional set of services provided by farmland complicates the task of identifying which farmland should be preserved. For this reason many states and local governments establish criteria to rank and select parcels of farmland for protection. This study examines whether criteria commonly used by state programs to guide purchases of agricultural conservation easements influence public demand for farmland preservation. The results provide policy makers with additional information to assess current ranking criteria that set the standard for farmland preservation.Land Economics/Use,

Assessing residence times of hyporheic ground water in two alluvial flood plains of the Southern Alps using water temperature and tracers

International audienceWater temperature can be used as a tracer for the interaction between river water and groundwater, interpreting time shifts in temperature signals as retarded travel times. The water temperature fluctuates on different time scales, the most pronounced of which are the seasonal and diurnal ones. While seasonal fluctuations can be found in any type of shallow groundwater, high-frequency components are more typical for freshly infiltrated river water, or hyporheic groundwater, and are thus better suited for evaluating the travel time of the youngest groundwater component in alluvial aquifer systems. We present temperature time series collected at two sites in the alpine floodplain aquifers of the Brenno river in Southern Switzerland. At the first site, we determine apparent travel times of temperature for both the seasonal and high-frequency components of the temperature signals in several wells. The seasonal signal appears to travel more slowly, indicating a mixture of older and younger groundwater components, which is confirmed by sulphate measurements. The travel times of the high-frequency component qualitatively agree with the groundwater age derived from radon concentrations, which exclusively reflects young water components. Directly after minor floods, the amplitude of temperature fluctuations in an observation well nearby the river is the highest. Within a week, the riverbed is being clogged, leading to stronger attenuation of the temperature fluctuations in the observation well. At the second site, very fast infiltration to depths of 1.9 m under the riverbed could be inferred from the time shift of the diurnal temperature signal

Assessing hyporheic zone dynamics in two alluvial flood plains of the Southern Alps using water temperature and tracers

International audienceWater temperature can be used as a tracer for the interaction between river water and groundwater, interpreting time shifts in temperature signals as retarded travel times. The water temperature fluctuates on different time scales, the most pronounced of which are the seasonal and diurnal ones. While seasonal fluctuations can be found in any type of shallow groundwater, high-frequency components are more typical for freshly infiltrated river water, or hyporheic groundwater, and are thus better suited for evaluating the travel time of the youngest groundwater component in alluvial aquifer systems. We present temperature time series collected at two sites in the alpine floodplain aquifers of the river Brenno in Southern Switzerland. At the first site, we determine apparent travel times of temperature for both the seasonal and high-frequency components of the temperature signals in several wells. The seasonal signal appears to travel more slowly, indicating a mixture of older and younger groundwater components, which is confirmed by sulphate measurements. The travel times of the high-frequency component qualitatively agree with the groundwater age derived from radon concentrations, which exclusively reflects young water components. Directly after minor floods, the amplitude of temperature fluctuations in an observation well nearby the river is the highest. Within a week, the riverbed is being clogged, leading to stronger attenuation of the temperature fluctuations in the observation well. At the second site, very fast infiltration to depths of 1.9m under the riverbed could be inferred from the time shift of the diurnal temperature signal

Net Buyers, Net Sellers, and Agricultural Landowner Support for Agricultural Zoning

Agricultural zoning and land use restrictions are long-standing approaches for controlling non-agricultural development. Agricultural landowners may contest agricultural zoning if they expect zoning to reduce land prices on restricted land. However, it is common to find agricultural landowners on both sides of this issue. A prevailing economic explanation for variation in landowner support is that the price effect of zoning varies across land parcels and therefore, zoning may increases the value of some lands zoned for agricultural use. In this paper, we provide an additional explanation for variation in agricultural landowner support. We use the concepts of net buyers and net sellers of land to suggest that the utility effect of changing land prices depends on an agricultural landowner's position in the agricultural land market. Hence, even in situations where all agricultural landowners expect zoning to reduce agricultural land prices, some subset of agricultural landowners - i.e., net buyers - may benefit. Survey data from agricultural landowners is used to model the probability that an agricultural landowner will support agricultural zoning. The empirical findings are consistent with our hypothesis that net buyers and net sellers of agricultural land will differ in their support for agricultural zoning.Land Economics/Use,

A lunar base reference mission for the phased implementation of bioregenerative life support system components

Previous design efforts of a cost effective and reliable regenerative life support system (RLSS) provided the foundation for the characterization of organisms or 'biological processors' in engineering terms and a methodology was developed for their integration into an engineered ecological LSS in order to minimize the mass flow imbalances between consumers and producers. These techniques for the design and the evaluation of bioregenerative LSS have now been integrated into a lunar base reference mission, emphasizing the phased implementation of components of such a BLSS. In parallel, a designers handbook was compiled from knowledge and experience gained during past design projects to aid in the design and planning of future space missions requiring advanced RLSS technologies. The lunar base reference mission addresses in particular the phased implementation and integration of BLS parts and includes the resulting infrastructure burdens and needs such as mass, power, volume, and structural requirements of the LSS. Also, operational aspects such as manpower requirements and the possible need and application of 'robotics' were addressed

The Cellular Structure of Selected Apple Varieties

Apple cultivars (Sauergrauech, Klarapfel, James Grieve, Granny Smith, Mcintosh, Robinette) which had different textures based on sensory and instrumental analysis (particularly in firmness and mealiness) were examined by conventional scanning electron microscopy (SEM), cold-stage SEM (cryoSEM) and confocal scanning laser microscopy (CSLM) using various preparative procedures. Advantages, lim itations and artifacts of each technique are discussed. SEM with glutaraldehyde-fixation and criticalpoint- drying produced minimal tissue distortion and the fracture pattern and appearance of mealy versus non mealy tissue was different. Freeze-drying unfixed tissue caused cell collapse and firm versus soft varieties could not be differentiated. Freeze-fracturing and cryoSEM of apple ti ssue with varying textures revealed the degree of cell adhesion between frozen hydrated cells. CSLM provided more information on the three-dimensional internal structure of intact fresh apple tissue and cell cohesiveness . Details of structural elements were enhanced by staining with acridine orange