scholarly journals Relative impacts of key drivers on the response of the water table to a major alley farming experiment

2009 ◽  
Vol 13 (11) ◽  
pp. 2095-2104 ◽  
Author(s):  
S. L. Noorduijn ◽  
K. R. J. Smettem ◽  
R. Vogwill ◽  
A. Ghadouani
Keyword(s):  
Standard Deviation ◽  
Water Table ◽  
Land Degradation ◽  
Large Scale ◽  
Root Water Uptake ◽  
Specific Yield ◽  
Annual Rainfall ◽  
Alley Farming ◽  
Groundwater Levels ◽  
The Mean

Abstract. Widespread clearing of native vegetation in Southwest Western Australia has led to land degradation associated with rising groundwater, secondary salinisation and waterlogging. Re-establishing deep-rooted perennial vegetation across parts of the landscape is one technique for managing land degradation. Alley farming is an agroforestry practice where multiple perennial tree belts are planted in alternation with traditional agricultural crops. To identify the best configuration (belt width versus alley width) for controlling rising groundwater levels and providing viable economic returns, a large scale experiment was established in 1995. The experiment contains seven different alley farming designs, each with transects of piezometers running across tree belts into adjacent alleys to monitor changes in the groundwater level. Two control piezometers were also installed in an adjacent paddock. Groundwater at the site is shallow (<3 m) and of poor quality (pH 3–5, Ec 2.1–45.9 mS cm−1) so root water uptake from the saturated zone is limited. Simple hydrograph analysis could not separate treatment effects on the water table response. Subsequent statistical analysis revealed that 20–30% of the variability in the water table data over the 12 year study period was attributable to the alley farming experiment. To futher investigate the effect of the experiment on groundwater response, additional hydrograph analysis was conducted to compare the trends in the control piezometers in relation to those located within the belts. A difference of 0.9 m was observed between the mean groundwater levels in the control piezometers and the mean levels in the perennial belt piezometers. For a mean specific yield of 0.03 m3 m−3 (standard deviation of 0.03 m3 m−3) this equates to an additional average annual water use of 27 mm yr−1 (standard deviation of 33 mm yr−1) by the perennial agroforestry system. It is concluded that declining annual rainfall is the principal control on hydrograph response at the site, whilst perennial biomass development has a lesser impact on water table depth.

scholarly journals The effect of changes in rainfall on the response of the water table to a major alley farming experiment

2009 ◽  
Vol 6 (3) ◽  
pp. 4563-4588
Author(s):  
S. L. Noorduijn ◽  
K. R. J. Smettem ◽  
R. Vogwill ◽  
A. Ghadouani
Keyword(s):  
Water Table ◽  
Land Degradation ◽  
Large Scale ◽  
Saline Water ◽  
Specific Yield ◽  
Annual Rainfall ◽  
Climate Trend ◽  
Alley Farming ◽  
Groundwater Levels ◽  
The Mean

Abstract. Widespread clearing of native vegetation in Southwest Western Australia has led to land degradation associated with rising groundwater, secondary salinisation and waterlogging. Land degradation can be controlled by re-establishing native deep rooted perennial vegetation across parts of the landscape. Alley farming is an agroforestry practice where multiple perennial tree belts are planted in alternation with traditional agricultural crops. To identify the best configuration (belt width verses alley width) for controlling rising groundwater levels and providing viable economic returns, a large scale experiment was established in 1995. The experiment contains seven different alley farming designs, each with transects of piezometers running across tree belts into adjacent alleys to monitor changes in the groundwater level. Two control piezometers were also installed in an adjacent paddock. At the site groundwater is shallow (<3 m) and of poor quality (pH 3–5, Ec 2.1–45.9 mS cm−1) and so root water uptake from the saturated zone is limited. Simple hydrograph analysis did not identify any treatment effects on the water table response. Subsequent statistical analysis revealed that 20–30% of the variability in the water table data over the 12 year period was attributable to the alley farming experiment. It was hypothesized that a climate trend (reducing annual rainfall over time) may be obscuring the effect of the experiment. To further investigate the effect of the experiment on groundwater response, further hydrograph analysis was conducted to compare the trends in the control piezometers in relation to those located within the belts. A difference of 0.9 m was observed between the mean groundwater levels in the control piezometers and the mean levels in the perennial belt piezometers. For a mean specific yield of 0.03 m3 m−3 this equates to a small additional water use of 27 mm yr−1 by the perennial agroforestry system. It is concluded that declining annual rainfall is the principal control on hydrograph response at the site. Perennial biomass development and perennial root development (both laterally and vertically) exert only a small influence on water table depth. The implications of this study indicate that alley farming has a limited ability to control a rising water table in low lying areas with a shallow saline water table.

Synchronous Issue of IR-Based Large Scale Volume Localization System

2014 ◽  
Vol 496-500 ◽  
pp. 1643-1647
Author(s):  
Ying Feng Wu ◽  
Gang Yan Li
Keyword(s):  
Standard Deviation ◽  
Mobile Robot ◽  
Large Volume ◽  
Large Scale ◽  
Image Acquisition ◽  
Mean Value ◽  
Network Synchronization ◽  
Localization System ◽  
Localization Performance ◽  
The Mean

IR-based large scale volume localization system (LSVLS) can localize the mobile robot working in large volume, which is constituted referring to the MSCMS-II. Hundreds cameras in LSVLS must be connected to the control station (PC) through network. Synchronization of cameras which are mounted on different control stations is significant, because the image acquisition of the target must be synchronous to ensure that the target is localized precisely. Software synchronization method is adopted to ensure the synchronization of camera. The mean value of standard deviation of eight cameras mounted on two workstations is 12.53ms, the localization performance of LSVLS is enhanced.

scholarly journals CLIGEN Parameter Regionalization for Mainland China

2021 ◽  
Author(s):  
Wenting Wang ◽  
Shuiqing Yin ◽  
Bofu Yu ◽  
Shaodong Wang
Keyword(s):  
Standard Deviation ◽  
Solar Radiation ◽  
Mainland China ◽  
Cumulative Distribution ◽  
Annual Rainfall ◽  
Stochastic Weather Generator ◽  
Critical Set ◽  
The Mean ◽  
Parameter Values

Abstract. Stochastic weather generator CLIGEN can simulate long-term weather sequences as input to WEPP for erosion predictions. Its use, however, has been somewhat restricted by limited observations at high spatial-temporal resolutions. Long-term daily temperature, daily and hourly precipitation data from 2405 stations and daily solar radiation from 130 stations distributed across mainland China were collected to develop the most critical set of site-specific parameter values for CLIGEN. Universal Kriging (UK) with auxiliary covariables, longitude, latitude, elevation, and the mean annual rainfall was used to interpolate parameter values into a 10 km × 10 km grid and parameter accuracy was evaluated based on leave-one-out cross-validation. The results demonstrated that Nash-Sutcliffe efficiency coefficients (NSEs) between UK interpolated and observed parameters were greater than 0.85 for all parameters apart from the standard deviation of solar radiation, skewness coefficient of daily precipitation, and cumulative distribution of relative time to peak intensity, with relatively lower interpolation accuracy (NSE > 0.66). In addition, CLIGEN simulated daily weather sequences using UK-interpolated and observed inputs showed consistent statistics and frequency distributions. The mean absolute discrepancy between the two sequences in the average and standard deviation of the temperature was less than 0.51 °C. The mean absolute relative discrepancy for the same statistics for solar radiation, precipitation amount, duration and maximum intensity in 30-min were less than 5 %. CLIGEN parameters at the 10 km resolution would meet the minimum WEPP climate requirements throughout in mainland China. The dataset is availability at http://clicia.bnu.edu.cn/data/cligen.html and http://doi.org/10.12275/bnu.clicia.CLIGEN.CN.gridinput.001 (Wang et al., 2020).

scholarly journals Reconstruction of baryon fraction in intergalactic medium through dispersion measurements of fast radio bursts

2021 ◽  
Vol 503 (3) ◽  
pp. 4576-4580
Author(s):  
Ji-Ping Dai ◽  
Jun-Qing Xia
Keyword(s):  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Mass Fraction ◽  
Large Scale ◽  
Intergalactic Medium ◽  
Radio Bursts ◽  
Local Principle ◽  
Relative Standard ◽  
Baryon Mass ◽  
The Mean

ABSTRACT Fast radio bursts (FRBs) probe the total column density of free electrons in the intergalactic medium (IGM) along the path of propagation through the dispersion measures (DMs) that depend on the baryon mass fraction in the IGM, i.e. fIGM. In this letter, we investigate the large-scale clustering information of DMs to study the evolution of fIGM. When combining with the Planck 2018 measurements, we could give tight constraints on the evolution of fIGM(z) from about 104 FRBs with the intrinsic DM scatter of $30(1+z) \rm pc\, cm^{-3}$ spanning 80 per cent of the sky and redshift range z = 0–3. First, we consider the Taylor expansion of fIGM(z) up to second order, and find that the mean relative standard deviation σ(fIGM) ≡ 〈σ[fIGM(z)]/fIGM(z)〉 is about 6.7 per cent. In order to alleviate the dependence on fiducial model, we also adopt non-parametric methods in this work, the local principle component analysis. We obtain the consistent, but weaker constraints on the evolution of fIGM(z), namely the mean relative standard deviation σ(fIGM) is 21.4 per cent. With the forthcoming surveys, this could be a complimentary method to investigate the baryon mass fraction in the IGM.

Water balance and the water-table in deep sandy soils of the upper south-east, South Australia

1960 ◽  
Vol 11 (6) ◽  
pp. 970 ◽  
Author(s):  
JW Holmes
Keyword(s):  
Soil Water ◽  
Water Table ◽  
South Australia ◽  
Soil Water Storage ◽  
Annual Rainfall ◽  
Wetting Front ◽  
Wet Season ◽  
The Mean ◽  
Upper South ◽  
Static Level

A water-table occurs at an average depth of 11.3 m below the surface in deep sand country of the upper south-east of South Australia (County Cardwell). By observing the depth to which water penetrated into the soil profile during the wet season, and the static level of the water in bore-holes, it was proved that the watertable was not replenished by local rainfall. In three years of records, the wetting front penetrated 6.0, 2.1, and 3.6 m on the average, and the soil water thus stored was all used by the prevailing vegetation, either natural mallee heath or lucerne. The performance of the vegetation growing on the deep sand in ability to resist drought was characterized quantitatively by the supply rate of soil moisture as a function of the soil water storage. It was estimated that the yearly potential evaporation for 1957 was 113 cm. The mean annual rainfall is about 50 cm. The ground-water comes, it is suggested, from intake areas about 40 km east of the area under study, where surface floodwaters accumulate in wet seasons. The quantity of water flowing through the aquifer at present is calculated to be about 37 m3/(metre width of strip)/year.

scholarly journals Fractional snow-covered area parameterization over complex topography

2014 ◽  
Vol 11 (8) ◽  
pp. 9791-9827
Author(s):  
N. Helbig ◽  
A. van Herwijnen ◽  
J. Magnusson ◽  
T. Jonas
Keyword(s):  
Standard Deviation ◽  
Snow Depth ◽  
Large Scale ◽  
Climate Models ◽  
Complex Topography ◽  
Climatic Regions ◽  
Snow Covered Area ◽  
Covered Area ◽  
Terrain Parameters ◽  
The Mean

Abstract. Fractional snow-covered area (SCA) is a key parameter in large-scale hydrological, meteorological and climate models. Since SCA affects albedos and surface energy balance fluxes, it is especially of interest over mountainous terrain where generally a reduced SCA is observed in large grid cells. Temporal and spatial snow distributions are however difficult to measure over complex topography. We therefore present a parameterization of the SCA based on a new subgrid parameterization for the standard deviation of snow depth over complex topography. Highly-resolved snow depth data at peak of winter were used from two distinct climatic regions, in eastern Switzerland and in the Spanish Pyrenees. Topographic scaling parameters are derived assuming Gaussian slope characteristics. We use computationally cheap terrain parameters, namely the correlation length of subgrid topographic features and the mean squared slope. A scale dependent analysis was performed by randomly aggregating the alpine catchments in domain sizes ranging from 50 m to 3 km. For the larger domain sizes, snow depth was predominantly normally distributed. Trends between terrain parameters and standard deviation of snow depth were similar for both climatic regions, allowing to parameterize the standard deviation of snow depth based on terrain parameters. To make the parameterization widely applicable, we introduced the mean snow depth as a climate indicator. Assuming a normal snow distribution and spatially homogeneous melt, snow cover depletion curves were derived for a broad range of coefficients of variations. The most accurate closed form fit resembled an existing SCA parameterization. By including the subgrid parameterization for the standard deviation of snow depth, we extended the SCA parameterization for topographic influences. For all domain sizes we obtained errors lower than 10% between measured and parameterized SCA.

scholarly journals Variability and trend analysis of rainfall data of Jhalawar district of Rajasthan, India

2016 ◽  
Vol 8 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Bhim Singh
Keyword(s):  
Standard Deviation ◽  
Trend Analysis ◽  
Coefficient Of Variation ◽  
Monsoon Rainfall ◽  
Annual Rainfall ◽  
Dry Period ◽  
South West ◽  
The Mean ◽  
Drought Occurrence ◽  
Sw Monsoon

An attempt has been made to study the variability and trends of annual and seasonal rainfall for the period of 38 years (1973-2010) for all seven tehsils of Jhalawar district of Rajasthan. The mean annual rainfall of the district was found to 910 mm with standard deviation 218 mm and coefficient of variation 24 per cent. Annual rainfall varied from about 831 mm in Khanpur to more than 1022 mm in the Pirawa tehsil of the district. The annual rainfall showed declined trend (-0.23 to -17.41 mm/year) in all seven tehsils of the district. The negative trends at Pirawa (17.407 mm/year), Manoharthana (11.595 mm/year) and Aklera (5.789 mm/year) are statistically significant at less than 0.001, 0.05 and 0.05 levels, respectively. During the study period maximum dry period was recorded during postmonsoon and winter. Also, for the entire 38 years period maximum dry months were recorded during December till April. August was normal month for about 87 per cent followed by July and June for about 84 per cent and 66 per cent respectively. It was evident that the onset of south-west (SW) monsoon took place in the month of June and chancesof drought occurrence during kharif season were very low. Hence, SW monsoon rainfall is found ideal for raising kharif crops like soybeans, urd, moong, jowar, maize, tomato, brinjal, chilli, okra, kharif onion, amaranth, rainfed green gram, red gram, castor, etc in the district.

scholarly journals Can Anthropization Govern the Variation in Water Table Levels, Water Flow and Carbon Losses? A Case Study in Tropical Mountain Peatlands an Serra Do Espinhaço Meridional, Minas Gerais, Brazil.

2022 ◽  
Author(s):  
Uidemar Morais Barral ◽  
Alexandre Christófaro Silva ◽  
Cristiano Christófaro ◽  
Camila Rodrigues Costa ◽  
Aparecido Penafort Filho ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Table ◽  
Protected Area ◽  
Total Mass ◽  
Minas Gerais ◽  
Specific Yield ◽  
Tropical Mountain ◽  
The Mean ◽  
Carbon Losses ◽  
Mountain Peatlands

Abstract Peatlands are ecosystems formed by organic matter (~ 15% of the total mass) and water (~ 85% of the total mass), and constitute a particular type of free aquifer. They perform important hydrological functions by storing excess water during rainfall events, contributing to the baseflow of its rivers throughout the year. Degradation affects the dynamics of the water table, which, in turn, can influence the decomposition of organic matter content and the release of carbon into its waters. Its water retention capacity may also be compromised and reduce the volume of water available downstream, especially in the dry season. The aim of this study was to evaluate the effects of anthropic interference on variations in groundwater, water storage, and carbon flow in two tropical mountain peatlands, located at the head of the Araçuaí River, in Serra do Espinhaço Meridional (SdEM), Minas Gerais, Brazil. Groundwater levels were installed in piezometers distributed on a peatland located in a protected area (Natural Park) (Protected - TP) and in a peatland located outside the conservation unit (Anthropized - TA). Data were analyzed considering the daily rainfall recorded by an automatic weather station installed in the study area. From the data on precipitation and water table level variation, the specific yield (Sy) in the two peatlands was calculated. The observed flows and the mean monthly Sy on each piezometer were correlated and their significance was verified using the t test (p <0.05). The relationship between the observed flow and the mean monthly values of Sy obtained for the piezometers were verified through multiple regression. The specific yield correlated significantly with flow in both peatlands (p < 0.05). Multiple linear regression showed a coefficient of determination (R2) of 0.92 in both peatlands, indicating a direct relationship between Sy and observed flow. The TP presented a 43% smaller variation in the water table, a 7% higher specific yield and a specific flow rate of 13% higher in relation to the TA. The peatland located in a protected area retains more water, with less variation in flow throughout the year, and has less carbon output in the water compared to the anthropized peatland. The results demonstrated that anthropization is causing degradation of the peatland, reducing its water holding capacity and accelerating its carbon losses. In the medium term, these effects may lead to a drastic reduction in flow in the upper course of the Araçuaí River.

scholarly journals Fractional snow-covered area parameterization over complex topography

2015 ◽  
Vol 19 (3) ◽  
pp. 1339-1351 ◽  
Author(s):  
N. Helbig ◽  
A. van Herwijnen ◽  
J. Magnusson ◽  
T. Jonas
Keyword(s):  
Standard Deviation ◽  
Snow Depth ◽  
Large Scale ◽  
Climate Models ◽  
Complex Topography ◽  
Climatic Regions ◽  
Snow Covered Area ◽  
Covered Area ◽  
Terrain Parameters ◽  
The Mean

Abstract. Fractional snow-covered area (SCA) is a key parameter in large-scale hydrological, meteorological and regional climate models. Since SCA affects albedos and surface energy balance fluxes, it is especially of interest over mountainous terrain where generally a reduced SCA is observed in large grid cells. Temporal and spatial snow distributions are, however, difficult to measure over complex topography. We therefore present a parameterization of SCA based on a new subgrid parameterization for the standard deviation of snow depth over complex topography. Highly resolved snow depth data at the peak of winter were used from two distinct climatic regions, in eastern Switzerland and in the Spanish Pyrenees. Topographic scaling parameters are derived assuming Gaussian slope characteristics. We use computationally cheap terrain parameters, namely, the correlation length of subgrid topographic features and the mean squared slope. A scale dependent analysis was performed by randomly aggregating the alpine catchments in domain sizes ranging from 50 m to 3 km. For the larger domain sizes, snow depth was predominantly normally distributed. Trends between terrain parameters and standard deviation of snow depth were similar for both climatic regions, allowing one to parameterize the standard deviation of snow depth based on terrain parameters. To make the parameterization widely applicable, we introduced the mean snow depth as a climate indicator. Assuming a normal snow distribution and spatially homogeneous melt, snow-cover depletion (SCD) curves were derived for a broad range of coefficients of variations. The most accurate closed form fit resembled an existing fractional SCA parameterization. By including the subgrid parameterization for the standard deviation of snow depth, we extended the fractional SCA parameterization for topographic influences. For all domain sizes we obtained errors lower than 10% between measured and parameterized SCA.

Estimation of natural groundwater recharge in the Aguascalientes semiarid valley, Mexico

2018 ◽  
Vol 35 (3) ◽  
pp. 268-276 ◽  
Author(s):  
Lilia Guerrero-Martínez ◽  
Martín Hernández-Marín ◽  
Thomas J. Burbey
Keyword(s):  
Groundwater Recharge ◽  
Water Table ◽  
Boussinesq Equation ◽  
Specific Yield ◽  
High Temporal Resolution ◽  
Groundwater Levels ◽  
The North ◽  
Vertical Hydraulic Conductivity ◽  
Recharge Rates ◽  
Aguascalientes Valley

Groundwater recharge (GWR) is analyzed and evaluated within the Aguascalientes Valley by means of a modified linearized Boussinesq equation and the Water Table Fluctuations (WTF) technique. These techniques use the specific yield, water table variations and the subsurface drainage of groundwater. The methodology is applied to the semiarid Aguascalientes valley, which contains a thick vadose zone. The combination of the analytical solution based on the Boussinesq equation and the WTF technique, allows the method to be applied in areas with deep groundwater levels, such as the Aguascalientes valley, without the need for high temporal resolution data. The data for the application of the method were provided by various government agencies and includes information on 145 wells positioned within the valley during the period 1985-2015. The specific yield and the transmissivity were integrated from the results of two previous investigations. Results indicate that the variation of recharge ranges from 0.86 to 525.69 mm/year in the analyzed period, with the highest recharge rates occurring in the north and center parts of the valley and is likely attributed to high specific yield and vertical hydraulic conductivity due to the presence of coarse permeable soils present in the area. Conversely, the lowest recharge rates were found to occur near the north and south borders of the valley.

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