Hydrologic Cycle Literature Review

CHAPTER 2

BACKGROUND & LITERATURE REVIEW

2.1 Hydrologic cycle

The physical process controlling the distribution and the movement of water are best understood in terms of the hydrologic cycle. A schematic of the hydrologic cycle for a nature environment is shown in figure (2.1). Figure 2.1: Hydrologic cycle (Adopted from Life Water Canada site)

The main hydrological cycle processes can be listed as the following:

Precipitation:

Precipitation in the form of rain, snow and hail comes from clouds.

Evaporation:

As water is heated by the sun, its surface molecules become sufficiently energized to break free of the attractive force binding them together, and then evaporate and rise as invisible vapor in the atmosphere.

Transpiration:

The process

In other words, predictor selection refers to the large scale model, the grid points of the model, and physical variable category. With the various availability of large-scale atmospheric models and output variables, the process of predictor selection has become more and more complicated. Many studies have scientifically evaluated the relevance of different predictors in terms of spatial area, variable types, or predictor model. Wilby et al. (2001) offer a talented solution by providing regression-based, automated tools for predictor selection in SD (Wilby and Dawson, 2007). But this model is better fit only if observational database for model calibration is fairly large (e.g., daily time series for more than a

Storm-clusters were identified and the total rainfall per storm-cluster were obtained. Data analysis including missing values, outliers, and double-mass curve were applied before the more formal time series analysis. They analysed the trend direction and other implications of climate change using Mann-Kendall test. The decreased trends of storm-cluster rainfall showed considerable increase in mean minimum temperature trends. Smadi and Zghoul (2006) inspected changes, trends and fluctuations in the total rainfall and number of rainy days at Amman Airport Meteorological station in Jordan for the period 1922-2003. During 1957, their statistical analysis identified a sudden change and shift in annual number of rain days and the average total rainfall. Salameh (2009) investigated precipitation records in Jordan during the last 4 decades. He analysed the impacts of decreasing precipitation on the availability of surface and groundwater. The outcome showed that 10% decrease in precipitation resulted in about 39% reduction of flood runoff, and a decrease in groundwater recharge of 16% in rain rich areas getting more than 500mm/y increasing to 59% in areas having reasonable precipitation of around