Huai River Basin (HRB) is an important food and industrial production area and a frequently drought-affected basin in eastern China. It is necessary to consider the future drought development for reducing the impact of drought disasters. Three global circulation models (GCMs) from Coupled Model Intercomparison Project phase 5 (CMIP5), such as CNRM-CM5 (CNR), HadGEM2-ES (Had) and MIROC5 (MIR), were used to assessment the future drought conditions under two Representative Concentration Pathways (RCPs) scenarios, namely, RCP4.5 and RCP8.5. The standardized precipitation evapotranspiration index (SPEI), statistical method, Mann-Kendall test, and run theory were carried out to study the variations of drought tendency, frequency, and characteristics and their responses to climate change. The research showed that the three CMIP5 models differ in describing the future seasonal and annual variations of precipitation and temperature in the basin and thus lead to the differences in describing drought trends, frequency, and drought characteristics, such as drought severity, drought duration, and drought intensity. However, the drought trend, frequency, and characteristics in the future are more serious than the history. The drought frequency and characteristics tend to be strengthened under the scenario of high concentration of RCP8.5, and the drought trend is larger than that of low concentration of RCP4.5. The lower precipitation and the higher temperature are the main factors affecting the occurrence of drought. All three CMIP5 models show that precipitation would increase in the future, but it could not offset the evapotranspiration loss caused by significant temperature rise. The serious risk of drought in the future is still higher. Considering the uncertainty of climate models for simulation and prediction, attention should be paid to distinguish the effects of different models in the future drought assessment.

Achieving accurate parameter calibration is a relatively difficult problem in development and application of physically based distributed hydrological models. In the current research, Morris' screening method (one factor at a time [OAT]) and an error evaluation calibration were jointly adopted for parameter sensitivity analysis (PSA) for a distributed hydrological model developed for a single mountainous terrain. The results indicated that (1) the order of sensitivity of the parameters for rainfall−runoff calculation is thickness of the first soil layer, coefficient of permeability, infiltration velocity, porosity, and coefficient of roughness; (2) the order of the parameters for snowmelt calculation is bulk transfer coefficient, temperature correction factor, and albedo of snow cover layer surface; and (3) the value change of each parameter of the first layer in the soil vertical profile mainly impacts the numerical value of discharge of the surface flow, while the value change of each parameter of the second layer impacts the numerical value of discharge of the surface flow less, but results in the peak misplacement to some extent. The results are expected to provide methodology references for PSA and calibration for the physically based distributed hydrological model which developed for mountainous or otherwise single terrain.

Water resource issues are a challenging area of research in semiarid regions of the world. The objective of the current study was to reveal the main characteristics of seasonal surface runoff for the semiarid western Heilongjiang Province of China. The Alun River Basin, which has hydrological and meteorological characteristics of the local region, was adopted as the study location. A distributed rainfall-runoff combined with snowmelt hydrological model was used to carry out the runoff calculation for the six years (2011–2016). The results indicated that: The mean annual runoff coefficient was 0.34; snowmelt runoff accounted for 2.2% of annual total runoff in 2011–2016; the main part of annual rainfall and runoff was concentrated in the rainy season from June to September, the proportions of rainfall and runoff in this period were 78% and 86% to that of the annual means of 2011–2016; the peak flow represents a decreased trend since 2013, and evidently decreased in 2015 and 2016; less annual precipitation complex with paddy field retention of rainwater and runoff led to the peak flow and annual runoff coefficient in 2016 were obviously lower than that of annual means of 2011–2016. The results are expected to provide the basis for rational development and utilization of surface runoff, and further researches on surface runoff and water resources of the semiarid western Heilongjiang Province of China.

Developing a distributed hydrological model that is applicable to a variety of topographies is a substantial challenge to the hydrological modeler. The primary objective of this study was to develop a distributed hydrological model that has a universal structure and an adjustable core module for small- and medium-scale basins under various topographical and hydrogeological conditions. By analyzing structural characteristics of soil vertical profile and general process of rainfall-runoff calculation under the different topographical conditions, a distributed hydrological model with universal structure was devised by combining the kinematic wave theory with the geographic information system (GIS)–based data on the topographical and hydrogeological conditions of target basins. Model validations were conducted through numerical simulation of the observed flow-discharge for the following three basins with varied topography: (1) the Liudaogou Basin, which is located in the region of the northern Loess Plateau and is abundant in hills and gullies; (2) the Alun River Basin, which flows through eastern Inner Mongolia and the western Heilongjiang Province; and (3) the Bukuro River Basin, which is located in Japan. The results indicated that acceptable simulation results for the rainfall-runoff process were achieved under varying topographical and hydrogeological conditions in each basin and that the calculation accuracy was within the allowable range according to the error criterion (error $<0.03$ ). The model exhibited relatively high efficiency, and the Nash-Sutcliffe efficiency (NSE) was more than 0.90. Structural universality and core module adjustability of the model are discussed and analyzed for applicability under various topographical and hydrogeological conditions. The results are expected to provide a methodological reference for further studies on the distributed hydrological model for small- and medium-scale basins with varied topographical and hydrogeological conditions.