*Biophysical Effects of Evapotranspiration on Steppe Areas: A Case Study in Naâma… DOI: http://dx.doi.org/10.5772/intechopen.97614*

evolution and which has affected all of the study region or national territory both north and south of the country. Analysis of rainfall data (1990–2014) highlights the nature of the significant decrease or increase in rainfall, which is a phenomenon of climate change. Analysis of the data shows a decreasing rainfall gradient from north to south. In the northern part of the high steppe plains (Naâma, Mécheria), the annual rainfall varies between 200 to 300 mm and in the south (Ain Séfra) the average annual rainfall is equal to 200 mm /year. In fact, precipitation is generally concentrated in the autumn season, especially in October in the form of downpours or thunderstorms. The variability of mean precipitation shows that for the 24-year series, 4 wet years recorded values below the annual average and 5 dry years. This latest drought was manifested by rainfall either too low or too irregular during the year. This period of drought has adverse effects on the steppe environment due to its long duration. The author Rognon [47] considers that a dry year has a different effect depending on whether it follows another dry year or a wet year. We know from the start that the rain regime is irregular in these steppe regions [48]. Several authors (Despois, [40] and Seltzer [29]), confirm this in their studies. The series of pluviometric observations is subdivided into two main periods, namely a rainy period from October to April with a maximum rainfall in October of around 25 mm, and a second dry period from June to August who's rainfall represents only 11% of the annual total (0 to 5 mm). On the other hand, the stations which are in the steppe domain present a structure of precipitation quite different from the Saharan domain. Indeed, if we consider the long series of Seltzer (1913–1938), precipitation is mainly concentrated in the winter season. Precipitation of the recent series (1990–2014), is generally concentrated in the autumn season, especially in October in the form of downpours or thunderstorms. The variability of the mean precipitation shows that for the series of 25 years, 8 years are considered as wet for the first period (1913–1938) and 4 years for the recent series (1990–2014), and 17 years are considered as years dry for the first period and 5 for the second period. In general, the rainfall remains low, irregular with strong inter-annual variations, it is heterogeneous in time and space, this irregularity of frequencies confirms the appearance of dry periods which raged in the region during the years 1992, 1995, 1998, 1999, 2001, 2002, 2004 and 2013. All the indicators converge towards a persistent drought, even if significant rainfall episodes occur they do not manage to fill the deficit to reverse the trend.
