جستجوی مقالات مرتبط با کلیدواژه "man" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

Now a day, long-term prediction of climate variables is necessary for climate change impact studies. Currently Global Circulation Models (GCM) are powerful tools to generate climate scenarios. These models are limited to capture the local climate due to their low spatial resolution. So, they cannot be directly applied for hydrological modeling in a catchment scale. In this research, first the trend of variables such as rainfall, radiation, maximum and minimum temperature were assessed for the base period with nonparametric Man-Kendall test. Second, these variables were downscaled by using the outputs of HADCM model and under three scenarios of A1, A2 and B1 which are accepted by IPCC(1971-2010) under three scenarios and their monthly changes were investigated for three periods of 2011-2030, 2046-2065 and 2080-2099 compared to the base predicted period of (1971-2010). All these scenarios showed almost similar results on precipitation shortage and increasing of solar radiation, minimum and maximum temperature over the future periods. As an example, the results of A2 scenario showed increasing of the annual mean, minimum and maximum temperature by 1.1, 3.2, and 4.6 °C, increasing of solar radiation by 0.07, 0.30 and 0.33 mJ m-2d-1 and decreasing precipitation by 16.4, 17.6 and 31.9 percent for these periods compared to the base period.

Area of land under irrigation has increased in the last decade due to the increasing population, need plenty of food and lack of surface water resources, this policy has changed soil and water uses. Rainwater enters soil through tracks and pores in soil surface and as hit to impervious layer make groundwater table. In previous years drought caused severe decrease in surface water resources and increasing use of groundwater which resulted in water table drawdown and decline of groundwater quality. Considering these points, and groundwater importance and role, groundwater quantity variation during 1998, 2002 and 2007 and qualitative factors changes include EC, Cl, Hco3, K, Mg, Na, So4, TDS, TH, pH and at the beginning and end of the period were studied in a part of Babol-Amol plain located in Caspian Sea Basin with GIS techniques and changes in each of the qualitative factors were determined with using Mann-Kendall exam. For groundwater quality data of 10 parameters including. The results show that water table drawdown is not considerable and there is relative improvement in water quality.

In this research study the daily and annually trends of precipitation in the central Kavir basin of Iran during 1951- 2007. The pixel data of daily precipitation from APHRODITE’s data base with a spatial resolution of 0.25˚ have been used. The Mann-Kendall (MK) nonparametric test has been used for determining the precipitation trend in this area. The trends have been tested in 3 levels 90%, 95% and 99%. This study illustrated that in confidence level of 99%, some area such as Loot Kavir had decreasing trend and some other area such as western and north heights of basin had rising trend of precipitation. But more than 80% of area doesn’t indicate any significant trend for annually precipitation in this 58 years period.