Watershed Management Research
Year:2010 | Volume:23 | Issue:2 (87)|Papers Count:10

Agricultural soils are valuable resources and their protection and fertility management play an important role in the sustainable agriculture. One of the suitable tools that make it possible to manage the soil fertility is the use of soil nutrients map. The main goal of this research is to study the spatial structure and mapping the spatial distribution of some soil micronutrients using geostatistics and GIS techniques. To do this research, 390 mixed soil samples along with their GPS-based coordinates were taken from Maragheh agricultural soils. Soil samples were analyzed and the amounts of EC, pH, %OC, P, K, Zn, Mn, Fe, Cu and B, were determined. For geostatistical analyses the elements semivariograms were developed and then the suitable theory model fitted to the experimental semivariograms. The information generated from the fitted models were applied to make use of ordinary kriging For estimating the value of microelements in the unknown locations. All above mentioned steps were performed in the GIS environment that resulted in generating soil fertility maps (zonation maps).

Chemical fertilizers are the main resources to supply plant nutrients and optimum use of them, have an important role in field of environmental sustainability and the agricultural products safety. In order to management of the fertilizers, there is necessary to know the soil nutrients amount that can supply the plants. Unrecognizing of the soil variability in different locations and the using unique amount of fertilizers may lead to over or under supplying of soil nutrients. This research was done to study of spatial variability of the soil macro-nutrients; N, P and K, comparing Geostatistics methods to estimate them and carrying out the related maps in order to fertilizer management in Uremia plain, W. Azarbaijan. To estimate fertilize elements; Organic Carbon, Phosphorus and Potassium on non-sampled points, Kriging, Co-Kriging and Weighted Moving Average methods were used by GS+ and GIS. To compare the applicability these methods the Cross Validation was used by MAE and MBE. Results showed that kriging method has the highest with %99 correlation coefficient and gausian semi-variorum, has high accordance to estimate the non-sampled points. There is also obtained the MAE=0.18 to 0.75 and MBE=-0.002 to 0.12 meq/100gr soil in this method

Optimal natural resources management depended on reliable as well as up-to-dated data. For this mean, land use/ cover maps are considered as an important source of information on the natural resources management. Nowadays, remote sensing users could be able to derive different land use/cover maps from satellite images by using specific interpretation techniques. Some characteristics of Satellite images such as: digitally format, production up-to dated data, wide viewing angle (swath width), multispectral as well as multi temporal and revisiting time of data acquisition with high speed on data transformation make those be considered as valuable information on the natural resources management. In this research, land use/cover map of study area has been produced based on digital interpretation of SPOT5 satellite image (2005) by Object Oriented method. Based on proposed methodology, some pre-Processing practices which involve geometric and radiometric correction were implemented by applying Pci Geomatica 9.1 software. Image processing was conducted on the next step based on Object Oriented method by applying eCogenation software. Followed step related to classifying of SPOT image based on proposed classes (18 classes: irrigated agriculture, dry farming area, bare soil, apricot orchards. Apple gardens, vineyards…). Finally, accuracy of classified image was assessed by fulfilling of error matrix and calculating of overall accuracy as well as Kappa Coefficient. Result of overall accuracy assessment was calculated 93.43%. It was confirmed the reliability of classification results. Final step was proposed to implement geo database into GIS environment for both illustration of produced map and comparing with former which was derived by pixel method. Results of this research showed, by Object-oriented method one be capable to produce land use/cover maps simultaneously with high accuracy and more classes.

Study of turbidity current hydrodynamics plays an important role in increasing the economical life of dams though reduction in sediment accumulation. In the present experimental study, the effect of entrance Froude number of turbidity current in sub and super critical conditions (Fr=0.6-3.5) have been tested through effect of change related to opening height of entrance gate on vertical distribution of flow velocity and sediment concentration under two dimensional flow conditions. The experiments were run in a 12 m-long by 0.2 m-wide by 0.5 m-high channel. Vertical distribution velocity was measured by Acoustic Doppler Velocitimeter (ADV). In present study the profile of concentration were computed through ABS method. The results show that due to increasing in height of opening entrance gate, the value of velocity in profiles increase. Also height opening entrance gate with the value of concentration in vertical distribution have the non-direct correlation. Also the results show that the equivalent height of average velocity is about 0.8 times of the depth-averaged thickness of the current. Furthermore, the results show that the equivalent height of average concentration is to be about 0.35-0.5 times the depth-averaged thickness of the current.

The current research was carried out to find the most effective environmental factors in plant species diversity. For this purpose, study was conducted in middle rangelands of Taleghan. Within each unit of sampling 4 parallel transects with 150m length, each containing 10 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area method. Soli samples were taken from 0-20 cm in starting and ending points of each transect. Measured soil properties included gravel, texture, organic matter, lime, pH, electrical conductivity, K, P and N. To determine the most environmental effective factors on plant diversity, PCA method was applied. The results indicated that slope, phosphorus, depth of soil play the main role in plant species diversity.

Gully erosion is one of the developed features of accelerated soil erosion which is known as a geomorphic threshold phenomenon and controlled by different environment factors. The main terms of these thresholds consist of: rainfall, hydraulic, pedology, landuse, topography and lithology. Most of researchers have used different criteria such as: shear stress, shear velocity, stream power and critical Froude number for investigation hydraulic threshold of rill and gully initiation. The most process based models for soil erosion prediction have used the 3.5 Pa for critical shear stress and consequently to assess their results it is necessary to having knowledge about hydraulic thresholds and effective factors on it in order to prevent over estimation. In this research an experimental flume was used to simulation flow in three landuse, dryfarming, range and abounded area, to investigate effects of land surface conditions on erosion and gully initiation. Results indicate that critical shear stress for soil erosion in rangeland; dryfarming and abandoned land are 83, 11 and 74 dyne/Cm2 respectively. In comparison to dryfarming in rangeland short vegetation cover causes to decrease the effect of ground cover on flow regime. However because of submergence condition during high discharge this effect was diminished in former landuse and incr4ease up to 25000. In addition in mean discharge the turbulence of flow in rangeland is less than other landuse which can be linked to effect of microtopography features in dryfarming area. Mean threshold shear stress for step initiation was calculated 192, 43 and 72 for range, dryfarming and abandoned area respectively. The main reason to explain this dramatic (3-4 times) variations is vegetation cover of soil surface. In fact this remarked decrease in dry farming land is related to effect of tillage practices on soil susceptibility and aggregate strength. Based on obtained results it can be drawn that using value of 35 dyne/Cm2 as critical shear stress in some process based models of erosion prediction is acceptable for sheet and rill erosion while for gully erosion these models are subject to serious uncertainty and unreliable estimation.

Determination of effective parameters on survivance of Atriplex canescens is essential for sustainable development of planted shrub areas. In order to, an experiment was carried out on limited area (4.5 ha) located at kavir-e- Siah koh of Yazd province. The location was planted by mentioned species in 1993. The experiment was conducted in split split plot design with 3 replications. The row spaces were 2, 4, and 6 meters in main plots. The periods of cutting including every one year, every two year, and every three year in sub-plots. In sub-sub plots 5 types of cutting height including 0, 20, 40, 60 cm and control were located. The mortality percentage of A. canescens was measured from autumn 1995 (before cutting) to autumn 2003.The maximum survival shrub’s densities was observed in 2 space treatments and the others were at the subsequent ranks. The cutting periods had significant effects on shrub mortality percentages to 6 old years (p<0.05), but had no significant effects in 9 old years. Therefore, every one year cutting of A. canescens had no negative effect on its survivance. Results indicated that the minimum mortality percentages of cutting height treatments was observed in no cutting shrubs and had no significant deference with 40 and 60 cm cutting height (p<0.05). In conclusion, annual grazing or cutting on mentioned shrubs above 40 cm cutting height have advantageous effects on growth, vigority and survivance.

Road network as the basis of forest management and road construction is one of the most important cost factor of investment. So, it is necessary to use different tools due to decreasing the expenses in planning and evaluating forest road network. Estimation of the volume of cut and fill operations is one of the time consuming and tiring parts in preparation of forest road project stages which can be used as an important construction cost factor and applied as a criterion for evaluating of road network variants. The objective of this study is Using GIS in estimation of the volume of cut and fill operations and investigating its rectification with ground truth through field measurement. This study was carried out in Chelir district of Kheiroud forest. Firstly a digital elevation model (DEM) was derived and was used to provide terrain data. Then a road network regarding technical principles and forestry necessities were designed using PEGGER (an extent ion for Arc view software) and digital topographic maps. Afterwards the volume of cut and fill operations was calculated in GIS environment. In order to testing the calculated volume operations in GIS environment, the road network was checked in the forest and the side slope was measured at every 100 meters. Using side slopes which were measured in 11/4 KM of road length, 115 cross-profiles were drawn. The volume of cut and fill were estimated by two manual and digital methods and were compared by paired samples T Test. The results suggested a significant difference between two methods.

In a river bend transport of sediment from the outer bank to the inner bank causes that the point bars developed in the inner bank and thus a convergence bend is created, Because of this the flow pattern will be different compare to the normal bend, Previous studies on the intake on a normal bend have shown that the best intake angle in the 60 degree location of the normal bend is 60 degrees, In order to investigate that this founding can be apply for a convergence bend or not, this study was conducted, To reach such goal experimental tests were conducted in a 90 degree convergence bend, The intake was installed in 60 degree location of the bend and the rate of intake discharge and sediment were measured under different subcritical flow conditions, The flume bed was covered by uniform sediment of 1 mm, All tests were conducted under live bed conditions, It was found from these tests that the discharge ratio decreases as the flow Froude number increases and for any Froude number, it increases when the intake angle changes from 30 to 45 degree and then is reduced as the intake angle increases, The sediment ratio also increases when the Froude number increases, For any Froude number the sediment ratio for the 45 degree intake angle is less than the other intake angles which were tested.

For assessing of rangelands and programming for supply of feedstock requirement of livestock depends to growth season and calculation of grazing capacity, the knowing of forage quality information of the key plants is necessary. This research was done in watershed of Taleghan, Nine species belonged to three life forms during three stage of growth assessed in this research including: Bromus tomentellus, Agropyron intermedium, Dactylis glomerata from family of Poaceae and Artemisia aucheri, Achillea millefolium, Centaurea virgata, Scariola orientalis from family Asteraceae and Thymus kotschyanus from family of Lamiatae and Coronilla varia from family of Fabaceae. Samples from species were collected randomly in three phenological stages (Vegetative growth, flowering and seeding). For each species 3 replicates and for each replicate five stands of plant were selected and cut from 1 cm above surface for grasses and forbs and current year growth for shrubs. The samples were dried in 70o oven for 24 hours. Then chemical analysis was accomplished for determination of: crude protein (CP), acid detergent fiber (ADF), digestible dry matter (DMD) and metabolic energy (ME). Analysis of variance was applied for data analysis. The results indicated that crude protein was decreased by development of growth in all species while acid detergent fiber increased. The highest amount of forage quality was related to Coronilla varia and in vegetative growth. While the lowest one is related to Centaurea virgata and in maturity growth. Also the results showed that there are significant differences between life forms and between species within life forms and between phenological stages (p£0.1). Also there were significant differences interaction effects species in phenological stages for total studied traits (p£0.1). Considering difference of forage quality of species and effect of phenological stages based on plant composition and time of grazing daily requirement of livestock will be different.