فصلنامه حفاظت منابع آب و خاک
سال هشتم شماره 3 (پیاپی 31، بهار 1398)

Applying proper irrigation management can reduce the yield loss caused by salinity. Growth responses of Seashore Paspalum, in terms of shoot and root lengths, fresh and dry weights, and the general quality of the grasses were studied hydroponically in a greenhouse under rotational levels of salinity stress. The experiment was arranged as a split plot based on randomized complete block design with four replications. Treatments include of five constant salinity levels as 5, 10, 20, and 30 gr/lit (named as Ctrl, C10, C20 and C30, respectively) as well as four more rotational salinity treatments (named as A10, A20 and A30). The results showed the maximum length of root and shoot (16.67 and 6.91 cm, respectively) was observed in Ctrl. At each salinity level, dry weight and fresh weight of shoot significantly increased in grasses grown under rotational salinity/control condition compared to their corresponding treatments under constant salinity stress condition. The percent of relative water content was higher in Ctrl, C10, A10 and A20. Also, C20 and C30 have the lower relative water content. Maximum water use efficiency observed at the Ctrl and then in A20 and A30. It concludes that rotational use of saline water causes improvement of WUE in grass.

GDP is one of the most important economic indicators at regional and national levels. Regarding climatic conditions, in most regions of Iran, production without irrigation is not economic. Hence, the analysis of irrigation sector share in total agricultural production and estimation of economic value that is associated to irrigation process is necessary. In this research, the gross value of irrigated agricultural products in Qazvin province (garden and annual crops) was calculated based on the methodology provided by the National Center for Statistics of Australia. So, irrigated and rainfed products were analyzed during the period from 2002 to 2016. The results showed, gross value of irrigated agricultural products of province in 2016 was 29491 billion Rials and equal to 95 percent of the total gross value of agricultural products. Irrigated grapes, wheat and tomatoes were rank first to third crops based on GVIAP index with 20%, 8%, 7% of gross value of irrigated agricultural productions in province. Also, based on the amount of consumed water by the products, the share of each cubic meter of irrigation water in the gross value was calculated 15259 Rials. Analysis of water use pattern showed that alfalfa with 5% share in gross value has the highest share in water use pattern (18%). In order to mitigate the economic consequences of water shortage in the agricultural sector, consideration of the GVIAP index and water use pattern can be recommended.

In this study, the Huff curves were extracted using the 418 events in the four selected stations. Firstly, the total storms were classified into the four distinct classes according to their durations including i) 0-2, ii) 2-6, iii) 6-12 and more than 12 hours. Then, the Huff curves were plotted for the 10%, 20%, … and 90% non-exceedance probabilities. Analysis conducted for each of the classes, separately, for the stations. Another Huff curve plotted using the all events in a unit class. Some statistical distributions commonly used in hydrology were utilized. The three indices (S2/10, I2/10, and Q2/10) calculated. The design hyetographs for each of the selected stations using the information of all events in a unit class prepared for 2 and 10-years return periods. The mathematical models of Huff curves derived as the Logistic model. The parameters estimated for all models. Results indicated that except Sarab, having the first quartile precipitation type, the three other stations had the second quartile types. The same results obtained for the class of storms with duration less than two hours. But for the classes of 2-6 and 6-12 hours, in some stations the type of precipitation shifted to the further quartile. The vertical distance of 50% and 90% Huff curves in the first, second and third quartiles shortened as the quartiles increases (S>I>Q). It was found that the Logistic model is capable in fitting the curves. The correlation coefficients between the observed and modeled values were found to be from 0.978 to 0.998.

The need to simulate rainfall time series at different scales for engineering purposes on the one hand and lack of recording such parameters in small scales because of administrative and economic problems, on the other hand, disaggregation of rainfall time series to the desired scale is an essential topic. In this study, for disaggregating the Tabriz and Sahand rain gauges time series, according to nonlinear characteristics of time scales, wavelet- Least Square Support Vector Machine (WLSSVM) hybrid model is proposed and daily data of four rain gauges and monthly data of six rain gauges from Urmia Lake Basin for ten years were decomposed with wavelet transform and then by using mutual information and correlation coefficient criteria, the subseries were ranked and superior subseries were used as input data of Least Square Support Vector Machine (LSSVM) model for disaggregating the Tabriz and Sahand rain gauges monthly rainfall time series to the daily time series. Results obtained from the WLSSVM disaggregation model were compared with the results of LSSVM and traditional multiple linear regression models. The results of WLSSVM model to LSSVM and multiple linear regression models at validation stage in the optimized case for Tabriz rain gauge were increased 10% and 37.5% and in the optimized case for Sahand rain gauge were increased 24.5% and 46.7% respectively. It was concluded that hybrid WLSSVM model has a higher accuracy than two other methods and can be considered as an accurate disaggregation model to disaggregate the rainfall time series.

In Iran, there are many investigations about landuse change which usually mention negative side. In this research landuse/land cover change trend investigate with use of landsat image and Markov chain in IDRISI Andes V15 software at the period of 1990, 2004 and 2018, and predicted changes for 2032 in Marvdasht region. There are about 196000 ha, equal to 91%, that used for cultivation, while range land, bare land and urban area are about 20000 ha, respectively 4.9, 2.7 and 1.6 percent of region area. In 28 years, from 1990 to 2018, agricultural and range lands decrease about 9%, while bare lands and urban area increased. At this period bare lands increased from 2.7% to 11.29% of the total region area. In general, the results of this study indicate that in the long-term, agricultural lands are declining and bare land is increasing, Hence immediate management plans are necessary to prevent the destruction of agricultural land.

In recent years, striking the balance between water supply and demand, reducing precipitation, climate change and, consequently, reducing surface water resources, the utilization of groundwater resources is more likely than past to be considered. Overuse and unmanaged use of groundwater resources in most plains of the country, especially in Hashtgerd Plain, has created a critical situation so that we can see the groundwater level decrease. Preservation of existing underground water resources, in a situation where the country is in a semi-arid region, in addition to providing water demands, in the landscape, it increases the hydrogeological potential of the soil. reduction in water levels will increase energy consumption and the cost of harvesting and extracting water, reducing water quality, land subsidence, increasing soil erosion and, more importantly, the emergence of a strategic water resource loss is increasing in the future. The purpose of this research is to manage and optimize the conjunction utilization use of surface water, underground and unconventional water in order to reduce the surface water deficit of Hashtgerd aquifer based on Integrated Water Resources Management to supply existing water demands, with the least harmful effects on the quality of groundwater resources and land capacities within the range.

Recently, the Lake Urmia has become one of the key dust sources in Iran due to a sharp drop in its water level. One of the essential information to decide how to deal with this problem is to know the distribution of the particles size carried at different heights above the soil surface. In order to trap the dust particles of the Lake Urmia area soils erosion, one of dust centers that was located in the southeastern of the Lake Urmia in 30 kilometers distance from the Tabriz-Azarshahr road was selected and the BSNE samplers (Big Spring Number Eight) were used. 14 pole, each of which had 4 samplers at 0.15, 0.5, 1 and 2 m heights above the soil surface were installed in a circle pattern. The samplers were evaluated in 12 interval periods (March 2016-February 2017) and the particle size distribution and the vertical profile of gathered particles were determined. Results showed that the amount of fine particles (0.15-0.053 mm) was greater than the coarse particles (1-0.25 mm). The highest amount of the fine particles was obtained at 100 and 200 cm and of the coarse particles was obtained at 15 cm height above the soil surface. When the height above the soil surface increased, the weight of gathered particles decreased. The power function was the best to explain changes between the weight of gathered particles and the height above the soil surface. There was a negative correlation between monthly rainfall and the weight of gathered particles.

Soil organic matter is considered as an indicator of soil quality and its fertility due to its impact on the physical, chemical and biological properties of soil. The purpose of this study was to investigate the effect of moisture on soil spectral behavior in order to estimate the amount of organic matter using visible-near infrared spectroscopy. Also, the performance of different preprocessing methods was compared in modeling. For this purpose, 50 soil samples from a surface layer (0-30 cm) were randomly collected from some cities in Tehran province. The samples were air-dried and passed through a 2 mm sieve. The amount of organic matter and soil texture were measured in the laboratory. To measure spectral reflectance, soil samples are dry in the oven and they were hydrated with levels of 5, 10, 15 and 20 wt.% (Grams of water / g of soil). Then, Soil samples were scanned using a FieldSpec Pro Spectroradiometer with a measurement range of 350–2500 nm. The results of the cross-evaluation indicated that SNV pre-processing method was better in predicting organic carbon content of soil. The best result for the validation group was obtained in dry oven moisture with R2 and RMSE values of 0.83 and 0.422 respectively. Also, R2 and RMSE were 0.75 and 0.543, respectively, at 5% moisture content, 0.70, 0.553 at 10% moisture, 0.605, 0.558 in moisture content of 15%.

Agricultural water footprint is more than 90 percent of fresh water resources in Iran. About 30 percent of it is used as feed for livestock. The livestock industry is one of the world's most water-based industries, especially in Iran. In this study, the mean livestock feed in the three provinces of Tehran, Alborz and Qazvin were estimated and then, using the Mekonnen and Hokkstra method, the water footprint was calculated. Then these values compared to the average water footprint in other countries (Netherlands, USA, Russia, Mexico, India and the world average). The values of virtual water footprint for producing beef were estimated 44.49, 45.18 and 45.51 m3/kg in milk production were estimated 2.24, 2.25 and 2.43 m3/Lit in Tehran, Alborz and Qazvin provinces respectively. The global average water footprints of beef and milk are 14.4 m3/kg and 1 m3/Lit. This comparision shows that the virtual water footprint in cattle production in Iran is higher than the global average. Based on the results of this study, the high water footprint in animal feed production and poor management of livestock farms are the main reseans of the high water footprint in Animal Production. Reducing water footprint in domestic forage production or forage imports is suggested due to the high contribution of nutrition to the high water footprint of beef and milk.