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Showing 4 results for Parametric Method
Qualitative Land Suitability Evaluation for Important Agricultural Crops of North Baraan Region in Isfahan Province
S. Ayoubi, A. Jalalian, J. Givi,
Volume 5, Issue 1 (4-2001)
Abstract

Qualitative land suitability evaluation is based on the physical parameters affecting the yield agricultural crops. The socio-economic factors are not considered in such evaluations. This study was carried out to assess the qualitative land suitability for irrigated wheat, barley, maize and rice in northern Baraan. Five soil series and 25 different phases were first delineated. Land utilization types commonly practiced in the region with intermediate input levels were considered. Physical requirements of the crops were determined and ranked using the available information. FAO framework and the proposed method of Sys were used for the evaluation. Qualitative evaluation was carried out according to both simple limitation and parametric methods by comparing land and climatic characteristics with crop requirements.

 It was shown that in addition to climatic factors, soil salinity, drainage and some soil physical properties such as texture, gravel and lime are the most limiting factors. Land physical suitability for rice production was very low in most land units. The results from physical evaluation by parametric method were very close to those from the simple limitation approach.


Land Suitability Evaluation for Irrigated Wheat in Falavarjan Region (Isfahan) Using Fuzzy Set Theory
J. Mohammadi, J. Givi,
Volume 5, Issue 1 (4-2001)
Abstract
This study aims to evaluate land suitability for irrigated wheat in Falavarjan region (Isfahan) using the theory of fuzzy sets. This method differs from the usual land evaluation procedures in its use of weight for different land characteristics and in its method of determining land suitability index. The results were compared with those from parametric land evaluation method. The correlation between land indices and observed yield was higher for the fuzzy set method (r=0.35) as compared to the parametric method (r=0.14). The higher relationship given by the fuzzy set method illustrates its potential usefulness and applicability to land evaluation.
Trend Analysis and Change Points in Stream Flow of Gorganrood Watershed
T. Mohammadi, V. Sheikh, A. Zare,
Volume 26, Issue 4 (3-2023)
Abstract
Trend analysis of stream flow provides practical information for better management of water resources on the eve of climate change. Therefore, the present study investigated river flow variations during three decades as well as projections of future discharge in the Gorganrood watershed. The Man-Kendall method has been used to detect the trend and methods of Pettitt, SNHT, and Buishand to identify points of a sudden change in discharge time series in 8 stations of Aq Qala, Galikesh, Gonbad, Haji Ghoshan, Nodeh, Ramyan, Sadgorgan, and Tamar. The Mann-Kendall trend test showed the existence of a significant negative trend (flow reduction) on a daily and annual scale in all stations. Monthly, the strongest negative trend in Aq Qala, Galikesh, Gonbad, Haji Ghoshan, and Ramyan stations was related to July, but in Nodeh and Tamar stations, it was related to August and February, respectively. A decreasing trend was observed in all stations on a seasonal scale, but this trend was not significant in some seasons. The results of the analysis of change points in discharge showed that the change points in the data used in this study are more of a decreasing and in some cases incremental type and some stations, no change points have been identified at all. Therefore, the number of decreasing changes in the studied hydrometric stations is significantly higher than the incremental changes and is more visible from 1993 to 1997 and 2005-2007 in three and four stations, respectively. Also, the most incremental changes among the stations are related to the Aq Qala station in 2017 with a flow rate of 234 cubic meters per second. Investigation of the flow of the basin in the past decades showed significant monotonic and abrupt changes which are mostly toward decreasing the basin’s discharge. The downward trend in discharge values at different time scales for all hydrometric stations of the Gorganrood watershed, which will be more severe in the future due to global climate change, and increasing the region's water needs for various future use due to population growth and the expansion of industries can also be considered as a serious warning for policymakers, planners, and local managers to prevent a possible water crisis in the region in the future with proper planning.

Trend Analysis and Change Points in Time Series of Water Level of Shallow and Deep Wells in Gorganrood Watershed
T. Mohammadi, V. Sheikh, A. Zare, M. Salarijazi,
Volume 27, Issue 3 (12-2023)
Abstract
A quantitative study of groundwater resources and accurate monitoring of changes over time, especially in areas facing limited water resources, is considered essential for proper management and sustainable exploitation of these resources. Golestan province, one of the semi-arid provinces of Iran has faced a drop in the groundwater level and an increase in the salinity of the groundwater due to the excessive withdrawals from the groundwater table and the reduction of atmospheric precipitation in the past few years. Gorgan Plain with an area of about 4727 square kilometers is one of the largest plains in Iran and the most important plain of Golestan province in terms of water supply for agricultural and drinking purposes. In this plain, there is a network of piezometers and observation wells that include continuous monthly measurements for more than 30 years. The objective of this research was to investigate the changes in the groundwater level of shallow (30 years (1989-2018)) and deep (22 years (1997-2018)) wells. The Man-Kendall method was used to reveal the trend and Pettitt, Normal Standard, and Buishand methods were used to identify sudden change points in a time series of groundwater levels in 49 shallow wells and 12 deep wells. The results of this research showed that the groundwater level in most of the studied wells had a significantly decreasing trend at a significant level of 5%. Also, the largest amount of groundwater loss was in the southern and southwestern parts of the plain, which can be attributed to a large amount of water taken from the wells due to their proximity to urban areas and some local conditions such as the proximity of the wells of this area are located in altitudes and at the entrance border of the aquifer. In the same way, as it rises, the fall decreases in the middle of the plain, and the amount of fall decreases in the northern areas and the edge of the Caspian Sea. It can be related to the proximity to the Caspian Sea and the high water table, and as a result, the inappropriate quality of water and land (high salinity and low fertility), which has caused the water withdrawal from this area to be less.

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