Subsurface hydrology, watershed hydrology, ecohydrology, field observation and modeling flow and contaminant transport in soil and aquifers, analytical, numerical, geostatistical, and stochastic methods in subsurface hydrology.
Zhang, Y.-K. and Schilling, K. 2005. Temporal Variations and Scaling of Streamflow and Baseflow and their Nitrate-Nitrogen Concentrations and Loads, Adv. in Water Resour., 28, p. 701-719, doi:10:1016/j.advwatres.2004.12.014.
Zhang, Y.-K. and Li, Z. 2005. Temporal scaling of hydraulic head fluctuations: Nonstationary spectral analyses and numerical simulations, Water Resour. Res., 41, W07031, doi:10.1029/2004WR003797.
Wang, L. and Zhang, Y.-K., An unconditionally-stable explicit scheme for groundwater flow equations, Computational Methods in Water Resources, XIV, 2002.