Specific yield of phreatic variation zone in karst aquifer with the method of water level analysis

Regime of groundwater level is a comprehensive reflection of the hydrogeological environment from the perspective of groundwater. Based on the analysis of the water-level change of 65 groundwater monitoring points from 1987 to 1990, it is found that intermittent cones of depression came into being due to groundwater exploitation in Guilin during the observation period. The buried depth of groundwater in the drawdown cones, the annual variation of water level and specific yield have higher values. Improvement has been made to the formula of infiltration coefficient of precipitation. By using the precipitation response data recorded at every 15 minutes for water level of No. 9 borehole which is near Zengpiyan Cave, the specific yield of phreatic variation zone is indirectly calculated by using the modified formula. The results are range from 0.012 to 0.462 and the spatial distribution of specific yield is ascertained. These make up the deficiency that empirical values cannot be categorized based on the actual conditions. What’s more, the widely used Aviriyanover’s empirical formula is poorly applicable to karst area. This is due to its strict requirement for outside conditions, such as shallow buried depth, homogeneous aquifer medium and small hydraulic gradient.

Groundwater evapotranspiration under psammophilous vegetation covers in the Mu Us Sandy Land, northern China

Groundwater is a significant component of the hydrological cycle in arid and semi-arid areas. Its evapotranspiration is an important part of the water budget because many plants are groundwater-dependent. To restore the degraded ecosystems, the need is pressing to further our understanding of the groundwater evapotranspiration（ET_g） in arid and semi-arid areas. This study employed the White method to estimate ET_g at four sites in the Mu Us Sandy Land in northern China, and the four sites are covered by Salix psammophila（SP site）, Artemisia ordosica（AO site）, Poplar alba（PA site）, and Carex enervis（CE site）, respectively. The depth of groundwater table and the duration of drainage were taken into account in calculating the specific yield（S_y） to improve the accuracy of the ET_g estimats. Our results showed that from late May to early November 2013 the ET_g were 361.87（SP site）, 372.53（AO site）, 597.86（PA site） and 700.76 mm（CE site）, respectively. The estimated ET_g rate was also species-dependent and the descending order of the ET_g rate for the four vegetation was： C. enervis, P. alba, A. ordosica, and S. psammophila. In addition, the depth of groundwater table has an obvious effect on the ET_g rate and the effect varied with the vegetation types. Furthermore, the evapotranspiration for the vegetation solely relying on the water supply from unsaturated layers above the groundwater table was much less than that for the vegetation heavily relying on the water supply from shallow aquifers.

Identification of Aquifer Properties in the Eastern Part of Kushtia District, Bangladesh

The present study has been undertaken to depict spatial distribution of different aquifer parameters in the eastern part of Kushtia district through a detailed hydrogeological survey. For this investigation, 119 lithologs and 92 pumping test data have been used. These data have been processed, analyzed, interpreted and krigged for the spatial assessment of the aquifer properties viz. transmissivity, hydraulic conductivity, hydraulic diffusivity, specific yield, radius of influence, and specific drawdown. It is seen from the investigation that the transmissivity and hydraulic conductivity values obtained from the pumping tests of the wells are varying from 1811 m2/day to 2568 m2/day and 32.5 m/day and 61.5 m/day respectively, the hydraulic diffusivity being ranging from 181,143 m2/day to 256,788 m2/day. The estimated specific yield of 17.97% - 23.46% supports that the area is dominated with coarse grained sands. This study reveals that the distribution of deep tube wells in the area are not within the radius of influence (638 - 760 m) each other, but few shallow and hand tube wells existed within the radius of influence. The estimated specific draw down is varying from 57 m/cumec to 126.1 m/cumec. From the overall analysis, it is found that the area is favorable for groundwater exploration.

Recharge Estimation of Hard Rock Aquifers under Sahelian Climate Conditions Using Water Table Fluctuation:Case Study of Tougou Catchment,Burkina Faso

This study aims to characterize water table fluctuations and estimate groundwater recharge in the Tougou catchment located in the Sahel zone of Burkina Faso. Water table fluctuation and groundwater budget approaches are developed on an experimental site equipped with observation wells. The trends of water fluctuations in the different layers of the weathering profile are similar. There is a time-lag response of groundwater recharge to the daily precipitation occurrences. The interaction between the upper (clayey alteration) and lower (transition zone-fractured schist complex) parts of the weathering profile shows that generally the hydraulic head in the upper part is higher than that of the lower part due to difference in drainage porosity. The latter varies at the catchment scale between 0.006 and 0.009 and is inversely proportional to the saturated thickness of the clayey alteration layer. The groundwater recharge is annually estimated between 36 and 49 mm, which correspond to 6% and 9% of mean annual rainfall in the catchment. Annual evapotranspiration was estimated to be about 223 to 443 mm.

Efficiency Analysis of Grid-connected Photovoltaic Power Plants

Analysis of photovoltaic power plant(PVPP)operations is important to both investors and users and to producers of equipment,researchers and designers as well.This paper presents the analysis of the year-long operations of the group PVPPs in Serbia connected to the distribution network which was carried out through specific indicators such as electric power generation,power,capacity factors,specific yield,losses,period of cost effectiveness of the investment,etc.Special attention has been paid to the influence of the azimuth and tilt of the photovoltaic modules on the performances of PVPPs.Results obtained through the year-long extensive measurements were compared to expected yields of PVPPs on the basis of the Climate SAF PVGIS application.The results of the analysis indicate that available software applications cannot always provide a good enough forecast of expected electric power production since they cannot always assess well enough the effects of the surrounding facilities on operations of a PVPP.In addition,it has been found that the correlation between losses of annual achieved specific yield of a PVPP and the azimuth is represented by a polynomial of the second degree,whereas the correlation between losses of the annual achieved specific yield of a PVPP and the tilt is represented by an exponential function.