جستجوی مقالات مرتبط با کلیدواژه « annual precipitation » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

The Improvement and development of predictions in ungauged catchments require recognizing effective factors and understanding the interactions between different components of the catchments and hydrological response in different climatic zones. The most important factors affecting the flow duration curve (FDC) indices are precipitation and its characteristics. Since the flow duration curve represents the hydrologic response of watersheds, investigating and recognizing the effect of rainfall distribution on it can help to identify predictive factors for estimating the flow duration curve in ungauged catchments. The purpose of this study was to analyze the relationships between the number of rainy days and the indices FDC in the different climate zones of the country. Catchments of each climatic region were separated using the climate map of the country and overlapping it with the four-level border map of the watershed, and 314 hydrometric stations with the common period (1976–2011) in six climatic zones were selected. Flow duration curve using daily stream flow data were extracted by the Hydro Office software (2015) and indices of Q2, Q5, Q10, Q15, Q20, Q50, Q75, and Q90 were selected. The average of rainy days for each catchment was calculated and the regression relations between the FDC indices and the average of the number of rainy days in different climatic regions were extracted and analyzed. The results showed that the correlation between the indices of the first part of FDC with the number of rainy days in all selected watersheds of climatic zones had a weak and unreliable relationship for prediction and estimation of FDC in the ungauged catchments. But the relationships for the end parts of FDC (Q75 and Q90), were strong. It is noteworthy that the average coefficient of determination for the low flow indices (Q75 and Q90) with the average annual rainy days in catchments of different climatic zones was approximately equal to 0.66. This indicates the importance of the parameter of the number of rainy days as the predictor of the low flow indices associated with the end part of the FDC in different climatic zones. Therefore, it is suggested that the number of rainy days should be used as a predictive parameter for estimating the indices of the end section of FDC; its use for estimating other indices is not recommended.

In this study, which lasted for 7 years due to two factors on annual precipitation and growing season precipitation ranges were Tang Laybid Yazd. The study area was the type of dominant vegetation types Artemisia aucheri. This type of plant was selected in three key. In every key area of 100 meters within 10 meters of each other transectbased and transect was placed on the slope 10 plots along each transect was calculated as 1 × 1 m square with a clear and proven choice and Available forage in each plot was measured by weighing and clipping method.. The results showed that the total amount of forage production with an annual rainfall level is 95 percent and The total yield of forage growing season with rainfall positive correlation. Rainfall during the growing season than other years was the appropriate rate will be higher yield

Forage quality is one of the most important affecting factors on the livestock performance which is affected itself by different parameters. In this research، four dominant and palatable range species were collected from Gorab Feraidonshar of Isfahan province in three phenological stages (vegetative، flowering and maturity) over two years (2007 and 2008). The plant species consist of Ferula ovina، Bromus tomentellus، Astragalus macruorus and Prangos uloptera. The samples were ground، and then nitrogen (N) and acid detergent fiber (ADF) were measured and the crude protein (CP)، dry mater digestibility (DMD) and metabolizable energy (ME) was estimated. Split plot design was used to analyze the data. Overall amount of crud protein، dry mater digestibly and metabolizable energy had significant differences in two years so that amount of these indices in 2007 (wet year with 725. 1 mm annual precipitation) was higher than those of 2008 (dry year with 284. 1 mm annual precipitation) in vegetative and flowering stages. However، amount of acid detergent fiber in 2007 was lower than that of 2008، but was not significance. In the maturity stage، significant differences were not found among the total indicators.