Possible Impacts of Global Warming on the Hydrology of the Ogallala Aquifer Region

The Ogallala or High Plains aquifer provides water for about 20% of the irrigated land in the United States. About 20 km³ (16.6 million acre-feet) of water are withdrawn annually from this aquifer. In general, recharge has not compensated for withdrawals since major irrigation development began in this region in the 1940s. The mining of the Ogallala has been pictured as an analogue to climate change in that many GCMs predict a warmer and drier future for this region. In this paper we attempt to anticipate the possible impacts of climate change on the sustainability of the aquifer as a source of water for irrigation and other purposes in the region. We have applied HUMUS, the Hydrologic Unit Model of the U.S. to the Missouri and Arkansas-White-Red water resource regions that overlie the Ogallala. We have imposed three general circulation model (GISS, UKTR and BMRC) projections of future climate change on this region and simulated the changes that may be induced in water yields (runoff plus lateral flow) and ground water recharge. Each GCM was applied to HUMUS at three levels of global mean temperature (GMT) to represent increasing severity of climate change (a surrogate for time). HUMUS was also run at three levels of atmospheric CO₂ concentration (hereafter denoted by [CO₂]) in order to estimate the impacts of direct CO₂ effects on photosynthesis and evapotranspiration. Since the UKTR and GISS GCMs project increased precipitation in the Missouri basin, water yields increase there. The BMRC GCM predicts sharply decreased precipitation and, hence, reduced water yields. Precipitation reductions are even greater in the Arkansas basin under BMRC as are the consequent water yield losses. GISS and UKTR climates lead to only moderate yield losses in the Arkansas. CO₂-fertilization reverses these losses and yields increase slightly. CO₂ fertilization increases recharge in the base (no climate change) case in both basins. Recharge is reduced under all three GCMs and severities of climate change.     

A predictive modeling approach to assessing the groundwater pollution susceptibility of the Paluxy Aquifer, Central Texas, using a Geographic Information System

The Paluxy aquifer in north-central Texas is composed primarily of Lower Cretaceous clastics. This aquifer provides water for both domestic and agricultural purposes in the region. The study area for this investigation incorporates the outcrop and recharge areas, as well as the confined and unconfined portions of the aquifer. The purpose of this investigation is to develop a predictive modeling approach for evaluating the susceptibility of groundwater in the Paluxy aquifer to contamination, and then compare this susceptibility evaluation to water-chemistry data collected from wells completed within the aquifer. Using such an approach allows one to investigate the potential for groundwater contamination on a regional, rather than site-specific scale. Based on data from variables such as land use/land cover, soil permeability, depth to water, aquifer hydraulic conductivity and topography, subjective numerical weightings have been assigned according to each variables' relative importance in groundwater pollution susceptibility. The weights for each variable comprise a Geographic Information System (GIS) map layer. These map layers are combined to formulate the final pollution susceptibility map. Using this method of investigation, the pollution susceptibility map classifies 32% of the study area as having low pollution susceptibility, 41% as having moderate pollution susceptibility, 25% as having high pollution susceptibility, and 2% as having very high pollution susceptibility. When comparing these modeling results with water-chemistry data from wells within the Paluxy aquifer, the four wells with the highest concentration of nitrate contamination are all found within regions of very high pollution potential. This confirms the accuracy and usefulness of the predictive modeling approach for assessing aquifer pollution susceptibility. Received: 1 June 1999 · Accepted: 30 August 1999     

南美洲白对虾全人工授精技术研究

于1988年4月和1991年4月分别从厄瓜多尔和美国引进南美洲白对虾仔虾,经驯化、养成和室内人工越冬后,采用单侧眼柄切除手术人工催熟,以试管授精和人工植荚方法进行该种的繁殖技术试验。结果表明,(1)体长在13—16cm的南美洲白对虾雌虾,一般在摘眼后的1—2周内开始性腺发育;产卵量通常为3—10万粒;产卵后的雌虾卵巢可再次发育,最高产卵次数高达19次。(2)应用高频电针法取荚的成功率和取荚后雄虾的存活率均为100％;用上述方法取得的精荚内的精子无需“获能”即可使卵子受精。(3)假裂现象在南美洲白对虾的未受精卵中较为普遍。     

Permeability Prediction for Low Porosity Rocks by Mobile NMR

Estimating permeability from NMR well logs or mobile NMR core scanner data is an attractive method as the measurements can be performed directly in the formation or on fresh cores right after drilling. Furthermore, the method is fast and non-destructive. Compared to T ₁ relaxation times, commonly measured T ₂ distributions are influenced by external and internal magnetic field gradients. We performed two-dimensional T ₁ and T ₂ relaxation experiments on samples of Rhaetian sandstone, a rock with low porosity and small pore radii, using a mobile NMR core scanner which operates within a nearly homogeneous static magnetic field. Because small pore sizes are associated with high internal magnetic field gradients, standard methods from NMR logging in the oil industry cannot be applied for accurate permeability prediction. Therefore, a new model theory was developed, which describes the pore radius dependence of the surface relaxivity ρ ₂ by both an analytical and a more practical empirical equation. Using corrected ρ ₂ values, permeability can be predicted accurately from the logarithmic mean of the T ₂ distribution and the physically based Kozeny-Carman equation. Additional core plug measurements of structural parameters such as porosity, permeability, specific inner surface area and pore radius distributions supported the NMR results.     

Modelled effect of changes in the CO2 concentration on the middle and upper atmosphere: Sensitivity to gravity wave parameterization

We have studied the temperature response to changes in the CO₂ concentration in the middle and upper atmosphere using the Coupled Middle Atmosphere–Thermosphere Model 2 (CMAT2). We have performed simulations with a range of CO₂ concentrations and three different ways of accounting for the effects of gravity waves, to allow for comparison with previous studies and sensitivity analyses. We initially find that the response of the model to the changes in CO₂ concentration which took place between 1965 and 1995 (320–360 ppm) is strongly dependent on the gravity wave parameterization that is used, but this is to a large degree due to steps or kinks in an otherwise nearly linear curve describing the temperature as a function of CO₂ concentration. We have not been able to identify the cause of these steps as part of the present study, which is a limitation and must be studied in future work. Here we treated the steps as model noise and rather focused on correcting for their effects by fitting straight lines to the temperature–CO₂ curves to estimate the overall slope of the curves. From these slopes we were able to obtain more robust trend estimates than can be obtained by comparing only two model simulations, as is normally done in other, similar studies. The corrected temperature responses to a 40 ppm change in CO₂ concentration still show up to 15–17% sensitivity to the gravity wave parameterization in the mesosphere and thermosphere. This remaining sensitivity is likely to be related to the fundamental differences in the way a change in temperature modifies the propagation and dissipation characteristics of gravity waves in each parameterization, which is particularly different for linear and non-linear schemes. The corrected trends we find are largely in agreement with other modelling studies, and therefore do not fully explain observed trends, which are typically larger than those predicted by modelling studies. However, modelling results could be similarly sensitive to other model parameters and settings, for example to gravity wave characteristics or solar activity level, and this should be further investigated as well.     

Development of a grid‐based version of the SWAT landscape model

Integrated river basin models should provide a spatially distributed representation of basin hydrology and transport processes to allow for spatially implementing specific management and conservation measures. To accomplish this, the Soil and Water Assessment Tool (SWAT) was modified by integrating a landscape routing model to simulate water flow across discretized routing units. This paper presents a grid‐based version of the SWAT landscape model that has been developed to enhance the spatial representation of hydrology and transport processes. The modified model uses a new flow separation index that considers topographic features and soil properties to capture channel and landscape flow processes related to specific landscape positions. The resulting model is spatially fully distributed and includes surface, lateral and groundwater fluxes in each grid cell of the watershed. Furthermore, it more closely represents the spatially heterogeneous distributed flow and transport processes in a watershed. The model was calibrated and validated for the Little River Watershed (LRW) near Tifton, Georgia (USA). Water balance simulations as well as the spatial distribution of surface runoff, subsurface flow and evapotranspiration are examined. Model results indicate that groundwater flow is the dominant landscape process in the LRW. Results are promising, and satisfactory output was obtained with the presented grid‐based SWAT landscape model. Nash–Sutcliffe model efficiencies for daily stream flow were 0.59 and 0.63 for calibration and validation periods, and the model reasonably simulates the impact of the landscape position on surface runoff, subsurface flow and evapotranspiration. Additional revision of the model will likely be necessary to adequately represent temporal variations of transport and flow processes in a watershed. Copyright © 2014 John Wiley & Sons, Ltd.     

The Past,Present and Future of the Great Steppe in the Context of Current Geopolitical Realities

<正>The modern geopolitical situation clearly demonstrates the development of two opposite directions.The first one includes the formation of a common global space,which unites the interests of individual countries that have similar political goals.The formation of the military alliance of NATO and countries of the European Union that seek to dominate in the world politics is a remarkable example of such     

Meridional Motions and Reynolds Stress Determined by Using Kanzelhöhe Drawings and White Light Solar Images from 1964 to 2016

Sunspot position data obtained from Kanzelhöhe Observatory for Solar and Environmental Research (KSO) sunspot drawings and white light images in the period 1964 to 2016 were used to calculate the rotational and meridional velocities of the solar plasma. Velocities were calculated from daily shifts of sunspot groups and an iterative process of calculation of the differential rotation profiles was used to discard outliers. We found a differential rotation profile and meridional motions in agreement with previous studies using sunspots as tracers and conclude that the quality of the KSO data is appropriate for analysis of solar velocity patterns. By analyzing the correlation and covariance of meridional velocities and rotation rate residuals we found that the angular momentum is transported towards the solar equator. The magnitude and latitudinal dependence of the horizontal component of the Reynolds stress tensor calculated is sufficient to maintain the observed solar differential rotation profile. Therefore, our results confirm that the Reynolds stress is the dominant mechanism responsible for transport of angular momentum towards the solar equator.