Search results for: Xiuyu Liang

Items from 1 to 14 out of 14 results

article

Effects of agricultural activities on the temporal variations of streamflow: trends and long memory

Chuke Chen, Yong Tian, You-Kuan Zhang, Xin He, more

Stochastic Environmental Research and Risk Assessment > 2019 > 33 > 8-9 > 1553-1564

Effects of agricultural activities on temporal variations in streamflow were investigated based on an integrated hydrological model in the Heihe River Basin (HRB). De-trended fluctuation analysis was conducted using the simulated time series of the daily streamflow at 13 observation points along the Heihe River. Both the original and deseasonalized streamflow were obtained and analyzed. We found that...

article

Contrasting NO₃-N concentration patterns at two karst springs in Iowa (USA): insights on aquifer nitrogen storage and delivery

Keith E. Schilling, Christopher S. Jones, Ryan J. Clark, Robert D. Libra, more

Hydrogeology Journal > 2019 > 27 > 4 > 1389-1400

Evaluating the patterns of NO₃-N concentrations at karst springs can be used to infer hydrologic processes and nutrient dynamics in karst aquifers. In this study, NO₃-N concentrations observed at two karst springs in northeast Iowa (USA) were evaluated for a 2-year period using high-frequency sensors. Despite similar watershed land use dominated by intense row cropping of corn and soybean production...

article

Assessing titanium dioxide nanoparticles transport models by Bayesian uncertainty analysis

Jin Liu, Xiankui Zeng, Jichun Wu, Xiuyu Liang, more

Stochastic Environmental Research and Risk Assessment > 2018 > 32 > 12 > 3365-3379

With the rapid growth of nanotechnology industry, nanomaterials as an emerging pollutant are gradually released into subsurface environments and become great concerns. Simulating the transport of nanomaterials in groundwater is an important approach to investigate and predict the impact of nanomaterials on subsurface environments. Currently, a number of transport models are used to simulate this process,...

article

Underdamped slug tests with unsaturated‐saturated flows by considering effects of wellbore skins

Xiuyu Liang, Hongbin Zhan, You‐Kuan Zhang, Jin Liu

Hydrological Processes > 32 > 7 > 968 - 980

An analytical solution is presented for the slug tests conducted in a partially penetrating well in an unconfined aquifer affected from above by an unsaturated zone. The solution considers the effects of wellbore skin and oscillatory responses on underdamped slug tests. The flow in the saturated zone is described by a two‐dimensional, axially symmetric governing equation, and the flow in the unsaturated...

article

Analysis of temporal variation and scaling of hydrological variables based on a numerical model of the Sagehen Creek watershed

Chen Yang, You-Kuan Zhang, Xiuyu Liang

Stochastic Environmental Research and Risk Assessment > 2018 > 32 > 2 > 357-368

Temporal variations of the main hydrological variables over 16 years were systematically investigated based on the results from an integrated hydrological modeling at the Sagehen Creek watershed in northern Sierra Nevada. Temporal scaling of these variables and damping effects of the hydrological system as well as its subsystems, i.e., the land surface, unsaturated zone, and saturated zone, were analyzed...

article

Analytical solutions of three-dimensional groundwater flow to a well in a leaky sloping fault-zone aquifer

Yuqing Zhao, You-Kuan Zhang, Xiuyu Liang

Journal of Hydrology > 2016 > 539 > C > 204-213

A semi-analytical solution was presented for groundwater flow due to pumping in a leaky sloping fault-zone aquifer surrounded by permeable matrices. The flow in the aquifer was descried by a three-dimensional flow equation, and the flow in the upper and lower matrix blocks are described by a one-dimensional flow equation. A first-order free-water surface equation at the outcrop of the fault-zone aquifer...

article

Effect of heterogeneity on spatiotemporal variations of groundwater level in a bounded unconfined aquifer

Xiuyu Liang, You-Kuan Zhang, Keith Schilling

Stochastic Environmental Research and Risk Assessment > 2016 > 30 > 1 > 1-8

Spatiotemporal variations of groundwater level due to a white noise recharge time series and a random transmissivity field in a bounded unconfined aquifer was studied. The analytical solutions for the variance and covariance of groundwater level were derived with non-stationary spectral analyses and superposition principle. It was found that the fluctuations of groundwater level are spatially non-stationary...

article

Co-Kriging Estimation of Nitrate-Nitrogen Loads in an Agricultural River

Xiuyu Liang, Keith Schilling, You-Kuan Zhang, Christopher Jones

Water Resources Management > 2016 > 30 > 5 > 1771-1784

Daily nitrate-nitrogen (NO₃-N) loads in the Raccoon River, Iowa, were estimated using Ordinary kriging (OK), Cokriging (CK), and a standard rating curve method (LOADEST) based on a dataset of 3451 measurements of NO₃-N concentration collected over 19 years. The CK estimation utilizes the temporal correlation of NO₃-N load with daily discharge and honors the measured points to improve estimation relative...

article

Effects of temporally correlated infiltration on water flow in an unsaturated–saturated system

Chen Yang, You-Kuan Zhang, Xiuyu Liang

Stochastic Environmental Research and Risk Assessment > 2016 > 30 > 7 > 2009-2017

Effects of temporally correlated infiltration on water flow in an unsaturated–saturated system were investigated. Both white noise and exponentially correlated infiltration processes were considered. The moment equations of the pressure head (ψ) were solved numerically to obtain the variance and autocorrelation functions of ψ at 14 observation points. Monte Carlo simulations were conducted to verify...

article

Analytical solutions for two-dimensional groundwater flow with subsurface drainage tiles

Xiuyu Liang, You-Kuan Zhang, Keith E. Schilling

Journal of Hydrology > 2015 > 521 > C > 556-564

The tile drainage problem in an unconfined aquifer was investigated. A mathematical model was established that describes two-dimensional groundwater flow in an unconfined aquifer near a river with a linearized Boussinesq equation, time-dependent sources and a sloped tile. Analytical solutions for groundwater level and discharge were derived and used to compare hydrologic conditions in a system with...

article

Analytic solutions to transient groundwater flow under time-dependent sources in a heterogeneous aquifer bounded by fluctuating river stage

Xiuyu Liang, You-Kuan Zhang

Advances in Water Resources > 2013 > 58 > Complete > 1-9

Analytical solutions for the water table and lateral discharge in a heterogeneous unconfined aquifer with time-dependent source and fluctuating river stage were derived and compared with those in an equivalent homogeneous aquifer. The heterogeneous aquifer considered consists of a number of sections of different hydraulic conductivity values. The source term and river stage were assumed to be time-dependent...

article

Temporal and spatial variation and scaling of groundwater levels in a bounded unconfined aquifer

Xiuyu Liang, You-Kuan Zhang

Journal of Hydrology > 2013 > 479 > Complete > 139-145

Temporal and spatial variation and scaling of groundwater level (h) due to a white noise source in an unconfined aquifer bounded by a no-flow boundary and a river were investigated with non-stationary spectral analyses. Analytical solutions for the variance (σh2), covariance (C _hh ), and spectrum (S _hh ) of h described by a linearized Boussinesq equation were derived and verified by...

article

Analytical Solution for Drainage and Recession from an Unconfined Aquifer

Xiuyu Liang, You‐Kuan Zhang

Groundwater > 50 > 5 > 793 - 798

One‐dimensional transient groundwater flow from a divide to a river in an unconfined aquifer described by the Boussinesq equation was studied. We derived the analytical solution for the water table recession and drainage change process described with a linearized Boussinesq equation with a physically based initial condition. A method for determining the average water table in the solutions was proposed...

article

A new analytical method for groundwater recharge and discharge estimation

Xiuyu Liang, You-Kuan Zhang

Journal of Hydrology > 2012 > 450-451 > Complete > 17-24

A new analytical method was proposed for groundwater recharge and discharge estimation in an unconfined aquifer. The method is based on an analytical solution to the Boussinesq equation linearized in terms of h ² , where h is the water table elevation, with a time-dependent source term. The solution derived was validated with numerical simulation and was shown to be a better approximation...

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