Mahin Kalehhouei; Raoof Mostafazadeh; Abazar Esmali Ouri; Rahmani Naneh Karan, Fardin; Fazeli, Alireza; Nazila Alaei; Zeinab Hazbavi
Abstract
Introduction
The rainfall system of a major part of Iran is mediterranean, where the precipitation amount during the vegetation period is low. In addition, the occurrence of precipitation in the non-vegetation period or beginning of the vegetation period, which does not cover the surface of the earth ...
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Introduction
The rainfall system of a major part of Iran is mediterranean, where the precipitation amount during the vegetation period is low. In addition, the occurrence of precipitation in the non-vegetation period or beginning of the vegetation period, which does not cover the surface of the earth well, is one of the important reasons for water erosion in Iran. Since vegetation has a special role in soil erosion control and runoff retention, any change in the vegetation structure and pattern, which expresses the landscape pattern and function, can have a significant effect on changing hydrological processes. Therefore, the assessment of soil and water loss and the quantification of its relationship with landscape metrics provide key information for the development of water and soil quality management strategies.
Materials and methods
The current research was conducted to investigate the hydrological component changes with landscape metrics on 2 m2 plots using simulated rainfall at an intensity of 32 mm.h-1 in a part of rangelands of Ardabil County. At first, considering the type and percentage of vegetation as the main variable, eight groups of vegetation composition along with one group without vegetation (control) were considered with three replications. The composition (and percentage) of the vegetation from the first to the eighth groups, respectively, include low-height graminea predominance (45), the composition of dense bushes with graminea (43), bushes with low-height and medium-distribution (37), sparse bushes mostly with low and medium height (31), the composition of sparse bushes with graminea (56), dense bushes in upper parts (54), low-height bushes with very low distribution (15), and dense bushes with almost uniform distribution (56). After measuring the runoff and sediment at the plot outlets, different hydrological components were calculated. Then, plots with nine different vegetation combinations were imaged in three replicates before and after rainfall simulation. After transferring the images prepared from the plots to the Arc/Map10.8 environment, nine important landscape metrics were calculated.
Results and discussion
Changes in the mean patch density (4.43-26.90), largest patch index (54.16-86.75), edge density (17.12-107.38), landscape shape index (1.50-4.47), mean shape area (4.16-37.46), mean Euclidean nearest neighbor distance (0.00-1.65), landscape division index (0.19-2.31), mean patch shape index (1.24-22.85), and the effective mesh size (15.80-43.96) indicate their different influence from different percentage and composition of vegetation cover. Spearman's correlation matrix analysis showed a nonsignificant relationship between the mean soil loss, runoff volume, runoff coefficient, and sediment concentration with landscape metrics (r<0.26 and p-value>0.10). The small scale of the studied plots, the lack of diversity in the vegetation composition, and the uniformity in terms of vegetation height can be cited as the reasons for the lack of correlation. In general, groups with vegetation values above 50% had a better condition in terms of LPI, AREA_MN, and MESH, which indicates more connectivity and less degradation. The increase in vegetation cover and spatial heterogeneity above the landscape surface can change the path of sediment transport, reduce sediment connectivity, and lead to a decrease in sedimentation.
Conclusion
The obtained results are applicable in explaining the appropriate reference to optimize water and soil protection measures on the watershed scale. However, It is suggested that similar and more comprehensive research be done in different scales of erosion plots and even in the landscape (slope) scale so that by considering a wide range of vegetation, topography, climatic conditions, as well as successive rains, it is possible to compare the results, optimum selection of study scale, and finally planning to manage and protect vegetation and water and soil resources.
Ali Nasiri khiavi; Raoof Mostafazadeh; Abazar Esmali Ouri; Omid Ghafarzadeh; Mohamad Golshan
Abstract
The hydrological regime of a river is the main influencing factor on the dynamics of river ecosystem and damming operations have a significant impact on river flow discharge. Therefore, the main objective of this research was to investigate the combined effects of changing climate variables and ...
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The hydrological regime of a river is the main influencing factor on the dynamics of river ecosystem and damming operations have a significant impact on river flow discharge. Therefore, the main objective of this research was to investigate the combined effects of changing climate variables and the Yamchi Dam construction on the discharge flow of the Balkhlu-Chai River in Ardebil using IHA Software 7.1 during the pre and after dam construction period (1973-2003) and (2004-2014). Toward this, the trend in the amounts of precipitation, temperature and evapotranspiration variables were evaluated using MAKESENS software. Then, the changes to 33 hydrological parameters and Range of Variability Approach (RVA) were firstly estimated. Subsequently, changes in the parameters of the flow rate in the periods before and after dam construction were investigated in the magnitude, duration, timing, frequency and rate of change categories. According to the results of trend analysis the precipitation had a significant decreasing trend, while, the temperature has been increased during the available time period. Based on the results, about 92% of the minimum flow discharge was attributed to that after the dam construction, while 25% of the maximum discharge belongs to this period, which indicates a decrease in the magnitude of discharge flow due to the dam construction and decreasing trend of rainfall. Also, the number of high flow pulses during the period of before dam construction was 38% higher than the period of after dam construction, while the number of low pulses in the period after dam construction was reduced by 60.7% compared to the period pre-dam construction. The value of Rise Rate index in the after-dam construction period is 0.11, but in the period before the dam construction is 0.3, which indicates a notable decrease in the mentioned indicator. Generally, based on the Magnitude group parameters, it can be concluded that the average amount of river flow during the period after the construction of the dam decreased by 52% compared with the period before the dam construction which lead to considerable environmental issue regarding the river ecosystem and flow condition. It should be noted that the variation in the hydrologic indicators is mainly influenced by the dam construction and also the change of climate variables has also been influential in this regard, and the separation of affecting factors need to be considered in further studies.
Roghayeh Asiabi-Hir; Raoof Mostafazadeh; Majid Raoof; Abazar Esmali-Ouri
Abstract
Availability and supplying adequate water is a fundamental prerequisite for socio-economic development of human societies. The purpose of this study was to evaluate the sustainability of surface water resources. The following criterion including resources (availability, variability), access (access to ...
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Availability and supplying adequate water is a fundamental prerequisite for socio-economic development of human societies. The purpose of this study was to evaluate the sustainability of surface water resources. The following criterion including resources (availability, variability), access (access to health), usage (domestic water use, agricultural water consumption), environment (baseflow, natural vegetation, environmental flow) and socio-economic capacities (literacy rates, the economically active population, employment in non-agricultural sector) were used to assess effective components on surface water sustainability in 21 sub-watersheds of Ardabil Province. The values of different criteria were standardized based on maximum method according to their numerical interval. The comparison of different water related components was provided using multi-dimensional spider-plots in the study area. The lowest and highest values of resource criteria (water per capita and rainfall coefficient of variations) were obtained in Shamsabad (16) and Hir (93) watersheds, respectively. The Nir, Pol-Almas, and Doostbeiglou watersheds having 60, 58, and 54 scores were identified as good condition, considering environment criteria and the other watersheds are critical. The capacity index had the highest and lowest values in Pol-Almas and Polsoltan watershed, respectively. Considering the access criteria, Shamsabad and Ahmad-Kandi watersheds had the highest and lowest scores, respectively. The mean standardized values of resource, usage, access, capacity and environment were 50, 60, 42, 38 and 25, respectively. In conclusion, the results showed that the access and resource criteria had the highest variations, and the environmental criteria were defined as undesirable conditions over the study area. It should be noted that the Central and Eastern parts of the study area had the same condition in terms of their criteria scores.
Khadije Haji; Raoof Mostafazadeh; Abazar Esmali-Ouri; Shahnaz Mirzaei
Abstract
Assessment of temporal and spatial variations of runoff and sediment is needed to sustainable management of watersheds, soil erosion and sediment control, and watershed conservation projects. The amount of discharge and sediment concentration rates were assessed in 15 river gauge stations located in ...
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Assessment of temporal and spatial variations of runoff and sediment is needed to sustainable management of watersheds, soil erosion and sediment control, and watershed conservation projects. The amount of discharge and sediment concentration rates were assessed in 15 river gauge stations located in the West-Azarbaijan Province in a 20-years recorded data using double-mass curve and annual variation analysis (coefficient of variations, annual distribution of regulating coefficient, and concentration rate). The logarithmic rating curve equation was used to sediment estimation according to the nature of discharge and sediment load variations. According to the results, the maximum discharge and sediment amount were observed in the May of spring season that can be related to the high amounts of snow melt and spring precipitation and associated high river flow discharge in the study area. The cumulative double mass curve of the runoff and sediment had a constant slope in the Pole-Bahramlou, Choplojeh, Sarighamish, Peighale, Naghadeh, Dorood, and Chapasabad stations, in which the sediment load is consistent with the runoff amounts. While, the decreasing pattern of sediment load was observed in the Dizaj, Urmia, Dashband, Ghasemlou, and Bayazidabad, which can be related to rainfall decrease and conservation measures (dam construction) and lower sediment amount in the study period. The highest coefficient of variation of runoff and sediment was observed in Pole-Bahramlou (16 and 173 percent), respectively. The highest monthly runoff-sediment uniformity was identified in Chaparabad station, where the lowest concentration rate of runoff and sediment were observed by 0.25 and 0.35 percent respectively; while, the Urmia station identified as a high rate of runoff and sediment concentration rate with 0.58 and 0.84 percent in the study area. It can be concluded that the seasonal variations of runoff and sediment had a consistent manner and some different spatial variations due to climatic, hydrologic and anthropogenic conditions.
