Maryam Azarakhshi; Jalil Farzadmehr
Abstract
Meteorological drought affects the water resources of the basin with a time delay, which leads to the occurrence of hydrological drought. Assessment of rainfall variability and drought is necessary to determine the existing water crisis and water resources management. This study was done in 42 watersheds ...
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Meteorological drought affects the water resources of the basin with a time delay, which leads to the occurrence of hydrological drought. Assessment of rainfall variability and drought is necessary to determine the existing water crisis and water resources management. This study was done in 42 watersheds of Khorasan Razavi province during 1975 to 2015 years to determine the temporal relationship between meteorological and hydrological drought. The hydrological drought severity was calculated with SDI index and meteorological drought was calculated with SPI index. The trend of precipitation and discharge was investigated with Mann-Kendall test. The temporal relationship between the mentioned indices was studied with Pearson correlation coefficient as simultaneously and with a time delay from one to 12 months. The results of Mann- Kendall test were indicative the negative trend of discharge in all watersheds and the most negative slop (-0.052) occurs in PolKhaton watershed. A combination of positive and negative trends in precipitation changes was observed in the study areas. However, the calculated positive trends were not significant at the 95% level in any of the watersheds. In 36.5% of the studied watersheds, no significant correlation coefficients were obtained at 95% level between SDI and SPI. In 60% of the studied watersheds, the highest correlation coefficient between precipitation and discharge with one-month delay, in 25% of watersheds without time delay, in 12.5% of watersheds with 2 months’ time delay and in 2.5% of watersheds with a time delay of 12 months were obtained.
Azam Tabarzadi; Meghdad Jourgholami; Alireza Moghaddam Nia; Baris Majnounian Garagiz; Pedram Attarod
Abstract
Many environmental challenges such as stormwater runoff and flood risk, chemical and particulate pollution of urban air, soil and water, the urban heat island, and summer heat waves are exacerbated in urban environments. Runoff from heavy rainfall in many parts of the world lead to erosion, sedimentation ...
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Many environmental challenges such as stormwater runoff and flood risk, chemical and particulate pollution of urban air, soil and water, the urban heat island, and summer heat waves are exacerbated in urban environments. Runoff from heavy rainfall in many parts of the world lead to erosion, sedimentation and transportation of elements that forest covers is the most important factor in controlling it. In this research, the qualitative and quantitative characteristics of runoff in Chitgar forest park have been investigated. For this purpose, runoff discharge, physicochemical parameters including total suspended solids, total dissolved solids, pH, and chemical parameters including calcium, magnesium, sodium, potassium, nitrate and phosphate were measured and analyzed during three storm events. The results of the present study indicated that the average values of the measured parameters were 1988.3 l / h, 40.64 mg/l, 2064.8 mg/l, 7.75, 2.95 mg/l, 2.23 mg/l, 584.4 mg/l, 5.71 mg/l, 1.36 mg/l, and 0.71 mg / l. Also, the correlation between parameters showed that there was a strong relationship between measured parameters, with the highest correlations between calcium with discharge (0.66) and total dissolved solids (0.69) and sodium with pH (0.7) and total dissolved solids (0.65). Comparison of the results obtained from this study and with those of other studies on water quality status of different rivers indicates that the qualitative pattern of urban runoff and also the relationships among the qualitative parameters of urban runoff are very different from surface runoff of rivers.
Aliakbar Nazari Samani; Hesam Heravi; Mehdi Panahi; Masoud Jafari Shalamzari
Abstract
Natural landscape alternation is a problem that has been under debate for a long time. Landutilization techniques like agriculture, forest and rangelands, residential and urban are amonginfluential criteria affecting erosion severity and sediment yield in a given region. In this respect,land management ...
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Natural landscape alternation is a problem that has been under debate for a long time. Landutilization techniques like agriculture, forest and rangelands, residential and urban are amonginfluential criteria affecting erosion severity and sediment yield in a given region. In this respect,land management is a promising option to mitigate it. Thus, acquaintance with quantitative soilerosion owing to land-use changes is of great importance for estimating disadvantages andlatent and intangible symptoms of erosion. Strategic planning for sustainable developmentcould be benefited from such knowledge. The current research considered a statistical periodfrom 1970 to 2004. This period was sub-divided into two separate periods from 1970 to 1987and from 1987 to 2004. During these periods, statistics relating to sedimentation, climatology(precipitation) and hydrology were analyzed. Results revealed that the sediment reduction inthese two periods under similar rainfall would be as a result of an increase in abandoned areas.
