Search

The study presents a daily water balance model with a focus on quantifying drought intensity and duration in different forest stands within the Level II monitoring sites in Saxony. The model requires climatic data input and various site and stand parameters, which mostly have physical meaning and can be measured. We estimated the van Genuchten soil parameters of the model by different pedotransfer functions. Water stress is assumed to occur when the relative extractable soil water (REW) or the ratio of real transpiration and potential transpiration or pressure head drops below a certain threshold. The model was not calibrated to test the robustness of physically based parameters but was validated with available soil moisture measurements at forest climate stations (grass vegetation) and inventory locations in various vegetation and climatic conditions with Kling-Gupta efficiencies > 0.5 at most of the sites. The model captures the dynamics of soil water depletion and recharge in a study period well. Day-to-day estimates of water balance components allow us to calculate the duration and intensity of drought events and derive stress indices. A dendro-ecological application is presented: a retrospective analysis of the effects of drought on radial tree growth. Some limitations and potential of applications of the model are discussed.

In order to relieve the water shortage for irrigation in North China, an adaptive real-time irrigation scheduling based on weather forecast and drought evaluation was developed. First, drought degree was evaluated into five ranks in crop growing seasons, and then the irrigation threshold was decided based on the chosen drought evaluation indexes, finally using field water balance principle and soil moisture simulation technology, an adaptive real-time irrigation scheduling was established to adapt to climate changes and actual rainfall based on winter wheat filed experiments from 2011 to 2014 in this study. Results showed that the irrigation water depths in 2013-2014 provided by the traditional irrigation schedule was 266 mm, which was much higher than that provided by adaptive real-time irrigation schedule (177 mm). Though the yield and water productivity provided by adaptive real-time irrigation were not the highest among different irrigation treatments, it is more suitable for the application adaptive real-time irrigation in North China to cope with the limited water resources of the irrigation districts. [ABSTRACT FROM AUTHOR]

Focusing on the shortages of moisture estimation and time scale in the self-calibrating Palmer drought severity index (scPDSI), this study proposed a new Palmer variant by introducing the Variable Infiltration Capacity (VIC) model in hydrologic accounting module, and modifying the standardization process to make the index capable for monitoring droughts at short time scales. The performance of the newly generated index was evaluated over the Yellow River Basin (YRB) during 1961–2012. For time scale verification, the standardized precipitation index (SPI), and standardized precipitation evapotranspiration index (SPEI) at a 3-month time scale were employed. Results show that the new Palmer variant is highly correlated with SPI and SPEI, combined with a more stable behavior in drought frequency than original scPDSI. For drought trend detection, this new index is more inclined to reflect comprehensive moisture conditions and reveals a different spatial pattern from SPI and SPEI in winter. Besides, two remote sensing products of soil moisture and vegetation were also employed for comparison. Given their general consistent behaviors in monitoring the spatiotemporal evolution of the 2000 drought, it is suggested that the new Palmer variant is a good indicator for monitoring soil moisture variation and the dynamics of vegetation growth. [ABSTRACT FROM AUTHOR]