Ground Water Level (ground + water_level)

Distribution by Scientific Domains


Selected Abstracts


Inflorescence characteristics, seed composition, and allometric relationships predicting seed yields in the biomass crop Cynara cardunculus

GCB BIOENERGY, Issue 3 2010
S. V. ARCHONTOULIS
Abstract Cynara (Cynara cardunculus) is a perennial C3 herb that has its potential as bioenergy crop. This paper aims (a) to derive empirical relationships to predict cynara seed yield per head and per unit area, avoiding laborious extraction of seeds from the complex structure of its inflorescences; (b) to determine the head-weight distribution per unit area, the seed composition and the oil profile of cynara seeds; and (c) to estimate the range of cynara biomass, seed and oil yield in representative parts of Greece. We analyzed 16 field experiments, varying in crop age and environmental conditions in Greece. Seed yield per head (SYhead) can be accurately predicted as a linear function of dry head weight (Hw): SYhead=0.429·Hw,2.9 (r2=0.96; n=617). Based on this relationship, we developed a simple two-parameter equation to predict seed yield per unit area (SY): SY=HN·(0.429·,,2.9), where , is the mean head weight (g head,1) and HN is the total number of heads per unit area, respectively. The models were tested against current and published data (n=180 for head-level; n=35 for unit area-level models), and proved to be valid under diverse management and environmental conditions. Attainable cynara seed yields ranged from 190 to 480 g m,2 yr,1, on dry soils and on aquic soils (shallow ground water level). This variation in seed yield was sufficiently explained by the analyses of head-weight distribution per unit area (small, medium and large heads) and variability of seed/head weight ratio at head level. Seed oil concentration (average: 23%) and crude protein concentration (average: 18.7%) were rather invariant across different seed sizes (range: 26,56 mg seed,1) and growing environments. [source]


Carbon dioxide balance of a fen ecosystem in northern Finland under elevated UV-B radiation

GLOBAL CHANGE BIOLOGY, Issue 4 2009
JAANA K. HAAPALA
Abstract The effect of elevated UV-B radiation on CO2 exchange of a natural flark fen was studied in open-field conditions during 2003,2005. The experimental site was located in Sodankylä in northern Finland (67°22,N, 26°38,E, 179 m a.s.l.). Altogether 30 study plots, each 120 cm × 120 cm in size, were randomly distributed between three treatments (n=10): ambient control, UV-A control and UV-B treatment. The UV-B-treated plots were exposed to elevated UV-B radiation level for three growing seasons. The instantaneous net ecosystem CO2 exchange (NEE) and dark respiration (RTOT) were measured during the growing season using a closed chamber method. The wintertime CO2 emissions were estimated using a gradient technique by analyzing the CO2 concentration in the snow pack. In addition to the instantaneous CO2 exchange, the seasonal CO2 balances during the growing seasons were modeled using environmental data measured at the site. In general, the instantaneous NEE at light saturation was slightly higher in the UV-B treatment compared with the ambient control, but the gross photosynthesis was unaffected by the exposure. The RTOT was significantly lower under elevated UV-B in the third study year. The modeled seasonal (June,September) CO2 balance varied between the years depending on the ground water level and temperature conditions. During the driest year, the seasonal CO2 balance was negative (net release of CO2) in the ambient control and the UV-B treatment was CO2 neutral. During the third year, the seasonal CO2 uptake was 43±36 g CO2 -C m,2 in the ambient control and 79±45 g CO2 -C m,2 in the UV-B treatment. The results suggest that the long-term exposure to high UV-B radiation levels may slightly increase the CO2 accumulation to fens resulting from a decrease in microbial activity in peat. However, it is unlikely that the predicted development of the level of UV-B radiation would significantly affect the CO2 balance of fen ecosystems in future. [source]


Evaluation of time-space distributions of submarine ground water discharge

GROUND WATER, Issue 3 2005
Makoto Taniguchi
Submarine ground water discharge (SGD) rates were measured continuously by automated seepage meters to evaluate the process of ground water discharge to the ocean in the coastal zone of Suruga Bay, Japan. The ratio of terrestrial fresh SGD to total SGD was estimated to be at most 9% by continuous measurements of electrical conductivity of SGD. Semidiurnal changes of SGD due to tidal effects and an inverse relation between SGD and barometric pressure were observed. Power spectrum density analyses of SGD, sea level, and ground water level show that SGD near shore correlated to ground water level changes and SGD offshore correlated to sea level changes. SGD rates near the mouth of the Abe River are smaller than those elsewhere, possibly showing the effect of the river on SGD. The ratio of terrestrial ground water discharge to the total discharge to the ocean was estimated to be 14.7% using a water balance method. [source]


Analytical Studies on the Impact of Land Reclamation on Ground Water Flow

GROUND WATER, Issue 6 2001
Jiu J. Jiao
Land reclamation has been a common practice to produce valuable land in coastal areas. The impact of land reclamation on coastal environment and marine ecology is well recognized and widely studied. It has not been recognized yet that reclamation may change the regional ground water regime, which may in turn modify the coastal environment, flooding pattern, and stability of slopes and foundations. This paper represents the first attempt to examine quantitatively the effect of reclamation on ground water levels. Analytical solutions are developed to study the ground water change in response to reclamation based on two hypothetical models. In the first model, the ground water flow regime changes only in the hillside around the reclamation areas. In the second model, the ground water regime changes in the entire hill. Both models assume that the ground water flow is in a steady state and satisfies the Dupuit assumptions. Hypothetical examples are used to demonstrate how the ground water level, ground water divide and ground water submarine discharge will change with the scale and hydraulic conductivity of the reclamation materials. The results show that the change of ground water regime depends mainly on the length of the reclaimed area and the values of hydraulic conductivity of the reclaimed materials. It is also seen that the reclamation may impact not only the ground water regime near the coast areas around the reclamation site, but also that in the coast areas opposite the reclamation area. A reclamation site near Tseung Kwan O in the New Territories in Hong Kong, China, is used as a case study to discuss the possible modification of the ground water system caused by reclamation. [source]


Modelling the hydrologic effects of dynamic land-use change using a distributed hydrologic model and a spatial land-use allocation model

HYDROLOGICAL PROCESSES, Issue 18 2010
Hone-Jay Chu
Abstract This study develops a novel approach for modelling and examining the impacts of time,space land-use changes on hydrological components. The approach uses an empirical land-use change allocation model (CLUE-s) and a distributed hydrological model (DHSVM) to examine various land-use change scenarios in the Wu-Tu watershed in northern Taiwan. The study also uses a generalized likelihood uncertainty estimation approach to quantify the parameter uncertainty of the distributed hydrological model. The results indicate that various land-use policies,such as no change, dynamic change and simultaneous change,have different levels of impact on simulating the spatial distributions of hydrological components in the watershed study. Peak flow rates under simultaneous and dynamic land-use changes are 5·71% and 2·77%, respectively, greater than the rate under the no land-use change scenario. Using dynamic land-use changes to assess the effect of land-use changes on hydrological components is more practical and feasible than using simultaneous land-use change and no land-use change scenarios. Furthermore, land-use change is a spatial dynamic process that can lead to significant changes in the distributions of ground water and soil moisture. The spatial distributions of land-use changes influence hydrological processes, such as the ground water level of whole areas, particularly in the downstream watershed. Copyright © 2010 John Wiley & Sons, Ltd. [source]


The possible hydrologic effects of the proposed lignite open-cast mining in Drama lignite field, Greece

HYDROLOGICAL PROCESSES, Issue 11 2008
Sotiris Panilas
Abstract The present study investigates the possible hydrologic effects of the proposed lignite open-cast mining in Drama lignite field (north Greece). Recent years have seen a rapid increase in surface mining. This activity has generated a growing concern for the potential environmental impacts associated with large scale surface mining. In order to achieve a safe mine operation and allow extraction of lignite to considerable depths, extensive dewatering by pumping will be necessary, while at the same time it is desirable to avoid presence of overpumping conditions in the broader area. Based on stratigrafic, hydrologic and hydrogeologic data, a three-dimensional finite difference model was developed in order to simulate the dewatering process of the western part of the lignite open-cast mine in Drama and to predict both spatially and temporally the decline of ground water level down to the lignite surface. The dewatering of the part of the aquifer which underlies the mine area will influence the hydrological conditions of the broader region. The most important anticipated effects will be the abandonment of shallow wells as well as the decrease of ground water pumping rates of deep wells. Aquifer discharge towards the ditches of the study area will cease and there will be an inversion of ground water flow from the ditches towards the underlying aquifer. Dewatering activities will probably result in minor subsidence of the nearby peat deposits of Drama Philippi marshes. Moreover, sand pumping as well as the presence of gasses is likely to cause local subsidence phenomena, mainly in the pit slopes. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Episodic stream water pH decline during autumn storms following a summer drought in northern Sweden

HYDROLOGICAL PROCESSES, Issue 9 2002
Hjalmar Laudon
Abstract The sources of episodic pH decline in four streams from northern Sweden during the autumn of 1996 were quantified. The events, in which pH dropped by between 1·0 and 2·4 units, were preceded by an extensive summer drought. Total organic carbon, which increased 100% to 160% during peak flow, was the most important driving mechanism of the episodic pH decline. Sulphate, however, was relatively more important during these autumn events than during spring flood. In the sites where past and present anthropogenic deposition were believed to be the main source of sulphate in stream water, sulphate contributed less than 0·3 pH units to the pH decline. In catchments where natural sources of sulphate are known to be important, sulphate contributed up to 0·6 units of pH decline. The export of sulphate during the episodes was two to nine times higher than what was expected from deposition only. The drought preceding the study episodes resulted in some of the lowest ground water levels during the 1990s in that region. The large export of sulphate was probably due to oxidation of natural sulphate bearing minerals in the soil and/or previously deposited sulphate driven by the low ground water level preceding the episodes. Copyright © 2002 John Wiley & Sons, Ltd. [source]


DECISION SUPPORT SYSTEM FOR MANAGING GROUND WATER RESOURCES IN THE CHOUSHUI RIVER ALLUVIAL IN TAIWAN,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2004
Chen Wuing Liu
ABSTRACT: Ground water is a vital water resource in the Choushui River alluvial fan in Taiwan. A significantly increased demand for water, resulting from rapid economic development, has led to large scale ground water extraction. Overdraft of ground water has considerably lowered the ground water level, and caused seawater intrusion, land subsidence, and other environmental damage. Sound ground water management thus is essential. This study presents a decision support system (DSS) for managing ground water resources in the Choushui River alluvial fan. This DSS integrates geographic information, ground water simulation, and expert systems. The geographic information system effectively analyzes and displays the spatially varied data and interfaces with the ground water simulation system to compute the dynamic behavior of ground water flow and solute transport in the aquifer. Meanwhile, a ground water model, MODFLOW-96, is used to determine the permissible yield in the Choushui River alluvial fan. Additionally, an expert system of DSS employs the determined aquifer permissible yield to assist local government agencies in issuing water rights permits and managing ground water resources in the Choushui River alluvial fan. [source]


Salinity-related desertification and management strategies: Indian experience

LAND DEGRADATION AND DEVELOPMENT, Issue 4 2009
G. Singh
Abstract High concentration of salts in the rootzone soil limits the productivity of nearly 953 million ha of productive land in the world. Australia, followed by Asia, has the largest area under salinity and sodicity. Most of the salt-affected soils and brackish ground water resources are confined to arid and semiarid regions and are the causative factors for triggering the process of desertification. The problem of salinity and sodicity has degraded about 6·73 million ha area in India. Secondary salinization associated with introduction of irrigation in dry areas like Thar desert in the western part of the country and Sharda Sahayak in Central India have caused desertification due to rise of salts with the rise in ground water level. Large scale cultivation of prawns using sea water in coastal Andhra Pradesh and elsewhere rendered about 2.1 million ha area unfit for agriculture. Similarly, 30,84 per cent ground water in north-western states of the country is either saline and /or brackish and is unfit for irrigation. Use of marginal quality water for irrigation has rendered several thousand ha of productive land unfit for cultivation. The Central Soil Salinity Research Institute was established in 1969 at Karnal to develop sustainable and eco-friendly technologies for reclamation and management of salt-affected soils and judicious use of marginal quality waters. The institute has developed location-specific techniques for reversion of salinity related desertification in India. Salient findings of research during the last three decades and more are presented in this review. This paper deals with (a) classification, nature and extent of salt-affected soils and poor quality water in India, (b) case studies/socio-economic concerns of salinity related desertification, (c) chemical, hydrological and biological approaches in use for rehabilitation of salt-affected soils, (d) guidelines for safe and productive use of marginal quality ground water through cyclic and mixed mode and precision irrigation techniques, (e) successful rehabilitation case studies, (f) alternate land use practices such as raising forest plantations, horticulture, agroforestry, high value medicinal, aromatic and flowering crops, etc., (g) technological, social, economic and environmental impacts and (h) future line of research. Issues requiring policy initiatives to halt salinity-related desertification are also discussed in this review paper. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Analytical Studies on the Impact of Land Reclamation on Ground Water Flow

GROUND WATER, Issue 6 2001
Jiu J. Jiao
Land reclamation has been a common practice to produce valuable land in coastal areas. The impact of land reclamation on coastal environment and marine ecology is well recognized and widely studied. It has not been recognized yet that reclamation may change the regional ground water regime, which may in turn modify the coastal environment, flooding pattern, and stability of slopes and foundations. This paper represents the first attempt to examine quantitatively the effect of reclamation on ground water levels. Analytical solutions are developed to study the ground water change in response to reclamation based on two hypothetical models. In the first model, the ground water flow regime changes only in the hillside around the reclamation areas. In the second model, the ground water regime changes in the entire hill. Both models assume that the ground water flow is in a steady state and satisfies the Dupuit assumptions. Hypothetical examples are used to demonstrate how the ground water level, ground water divide and ground water submarine discharge will change with the scale and hydraulic conductivity of the reclamation materials. The results show that the change of ground water regime depends mainly on the length of the reclaimed area and the values of hydraulic conductivity of the reclaimed materials. It is also seen that the reclamation may impact not only the ground water regime near the coast areas around the reclamation site, but also that in the coast areas opposite the reclamation area. A reclamation site near Tseung Kwan O in the New Territories in Hong Kong, China, is used as a case study to discuss the possible modification of the ground water system caused by reclamation. [source]


Episodic stream water pH decline during autumn storms following a summer drought in northern Sweden

HYDROLOGICAL PROCESSES, Issue 9 2002
Hjalmar Laudon
Abstract The sources of episodic pH decline in four streams from northern Sweden during the autumn of 1996 were quantified. The events, in which pH dropped by between 1·0 and 2·4 units, were preceded by an extensive summer drought. Total organic carbon, which increased 100% to 160% during peak flow, was the most important driving mechanism of the episodic pH decline. Sulphate, however, was relatively more important during these autumn events than during spring flood. In the sites where past and present anthropogenic deposition were believed to be the main source of sulphate in stream water, sulphate contributed less than 0·3 pH units to the pH decline. In catchments where natural sources of sulphate are known to be important, sulphate contributed up to 0·6 units of pH decline. The export of sulphate during the episodes was two to nine times higher than what was expected from deposition only. The drought preceding the study episodes resulted in some of the lowest ground water levels during the 1990s in that region. The large export of sulphate was probably due to oxidation of natural sulphate bearing minerals in the soil and/or previously deposited sulphate driven by the low ground water level preceding the episodes. Copyright © 2002 John Wiley & Sons, Ltd. [source]