This paper investigates optimal sampling times of drawdowns for the analysis of hydraulic tomography (HT) survey. The investigation was carried out by analyzing the spatial and temporal evolution of cross‐correlations between the head responses at an observation well and transmissivity (T) and storage coefficient (S) properties during a pumping test in homogeneous and heterogeneous aquifers. The analysis shows that the cross‐correlation between the head and S values is limited to the region between the observation and the pumping well in the aquifers: It reaches the highest value near the early time (t_m), and decays to zero afterwards. The time t_m is approximately equal to the time t₀ at which the extrapolated drawdown from the first straight line portion of an observed drawdown‐log time plot becomes zero. At early times, the high cross‐correlation between the head and T is confined to the region between the observation and the pumping well. This region then evolves into two humps: One on each side of the circular region encompassing the observation well and the pumping well. The size of the two humps expands and their values reach the maximum as flow reach steady‐state. As a consequence, we hypothesize that pairs of head data at t₀ and those at either the steady‐state or a late time during an HT survey could yield the best estimates of the heterogeneous T and S fields. Results from numerical experiments have verified this hypothesis and demonstrated that this sampling strategy is generally applicable even when the boundary condition is unknown. We, therefore, recommend in principle that (1) carrying out pumping tests of HT surveys for sufficiently long period of time such that drawdown reaches the entire area of interest and (2) using a constant head or zero drawdown for all boundaries during the inverse modeling analysis.

Weather and climate in a location are generally affected by global climatic phenomena. Monsoons and teleconnections are two climatic phenomena that have been assessed in specific regions for their correlations with regional precipitation. This study characterized the effects of monsoons and climate teleconnections on precipitation in eight climate zones across China. Correlations between monthly precipitation from 1951 to 2013 across the eight zones and each of two important monsoon indices [the Indian Summer Monsoon (ISM) and East Asian Summer Monsoon (EASM)] and two major teleconnection indices [El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)] were analyzed based on wavelet coherence and global coherence. The results demonstrated that on the annual timescale, monsoons have stronger effects than teleconnections on monthly precipitation in each of the eight climate zones. On the intra-annual (0.5–1 year) and inter-annual (2–10 year) scales, the ISM mainly affects precipitation in the East Arid Region, Northeastern China, Northern China, and Qinghai-Tibet Plateau; the EASM mainly affects Northern China, Central China, and Southern China; the ENSO mainly affects Western Arid/Semiarid region and Qinghai-Tibet Plateau; the PDO mainly affects the Western Arid/Semiarid region. On the decadal timescale, the ISM mainly affects the Western arid/Semiarid and Central China; the EASM mainly affects Western arid/Semiarid, Central China, and Qinghai–Tibet Plateau; the ENSO mainly affects Northeastern China and Central China; and the PDO mainly affects East arid and Southern China regions. These findings provide a practical reference for water resources management and/or for the prediction of precipitation in different regions of China.