Showing 150 results for Irrigation
Reza Aminpour, Sayed-Farhad Mousavi,
Volume 1, Issue 1 (4-1997)
Abstract
In order to determine the effects of number of irrigations on stages of development, yield, and yield components of cumin, an experiment was conducted in 1993 - 94 growing season with a randomized complete block design and four replications. The location of the experiment was Isfahan University of Technology Research Station in Shervedan Field. The irrigation treatments were: I1- Irrigation after planting I2- Irrigation after planting and at the stage of full standing of plants I3- Irrigation after planting, full standing of plants, and anthesis and I4- Irrigation after planting, full standing of plants, anthesis, and beginning of grain filling stage. The stages of development (from emergence to anthesis) occurred simultaneously in all treatments. However, the water deficit in I1 and I2 caused the plants to reach their physiological maturity 5 days sooner than the other two treatments. The time intervals between anthesis and physiological maturity in I4 and I3 treatments were 12 days and 5 days longer than those in the other two treatments, respectively. The grain yield of I1 and I2 were approximately 60% of I3 and no significant difference was observed between the grain yields of I1 and I2 treatments, nor between I3 and I4 treatments. The grain yields in I3 and I4 treatments were about 1742 and 1800 Kg/ha, respectively. The number of umbels per plant, the most important grain yield component, was greater in I3 and I4 than the other two irrigation regimes, but the number of seeds per umbel and 1000-seed weight of I3 and I4 were lower than that in I1 and I2 treatments.
Mohammad Reza Yazdani, Sayed-Farhad Mousavi,
Volume 1, Issue 2 (10-1997)
Abstract
Water requirements of paddy fields in the Gilan Province are provided for by a large irrigation network including Sepidrud reservoir dam, Tarik diversion dam, Fumanat network, Sangar diversion dam, and Sangar right and left canals. Because of the deposition of sediments in the Sepidrud reservoir, its capacity has been reduced profoundly. To overcome this problem, sediments are flushed in the second half of each year. The sediments coming from erodible surfaces of the Sepidrud watershed area out flowing from the dam in the spring, and the deposited sediments in the Sepidrud river in the second half of each year are a great hazard for the irrigation network. The objective of this research is to study the effect of the sediments on Sepidrud network. In this research, sediment data from the hydrometric station near Sepidrud dam were analyzed. Sediment samples were collected by a hand sampler (type DH-48) from Tarik and Sangar diversion dams, upper and lower ends of Sangar desilting basin, BP4 and SP3 canals, and field ditches and drains. Water discharge was measured by a current meter. Deposited materials in irrigation structures were sampled for grading. The results from this study indicate that the Sepidrud river and Tarik diversion dam deposit sediments at low discharges, but at high river discharges these sediments were found to he erodible. Average efficiencies of left and right desilting basins of Sangar diversion dam were 15.3% and 11.2%, respectively. The area located in Fumanat section, which receives water from Tarik diversion dam, requires desilting structures. The irrigation structures of the network are in danger of sediments. The main and the secondary canals, compared with 3rd and 4th order canals, have less settled sediments in them.
Teymour Sohrabi, Reza Asilmanesh,
Volume 2, Issue 2 (7-1998)
Abstract
Irrigation systems may or may not be well designed and properly used. Therefore, it is necessary to study these systems to provide direction to management in deciding whether to continue existing practices or to improve upon them. The major objective of this study is to determine the evaluation factors of center-pivot irrigation system and factors which usually affect irrigation performance. A solution. for the improvement of irrigation water use will be presented and design and management problems, will also be mentioned. To achieve the objectives of this study, the characteristics of the soil and the growing plant (seed corn) along with design parameters were determined. The system was designed on the basis of soil and the growing plant characteristics in the 500-ha farm of Ministry of Agriculture (located in the North East of Meshkinabad, Karaj) having a silty loam texture. Then, it was examined with respect to the existing conditions. Four radial rows of catch containers spacing 6 meters were set up and then field data for performance evaluation of system were determined. The evaluation factors were calculated on the basis of field data analysis. The results obtained are as follows: During the growing season, the average PELQ, AELQ and DU for the center-pivot system were about 79, 75.8 and 84 percent, respectively. Analysis of evaluation factors indicated that the system is not efficient DU and PELQ values were not high enough for the system because it was not properly designed for the existing conditions. Al the same time, it seems that the difference between PELQ and AELQ values are meaningful which may indicate management difficulties.
Behrouz Mostafazadeh, Sayed-Farhad Mousavi, Mohammad Hossain Sharif-Bayanolhagh,
Volume 2, Issue 3 (10-1998)
Abstract
To determine the effects of field slope, emitter discharge, irrigation water volume and soil texture on soil moisture profile and soil surface wetted shape from a point source, field data were collected on three different soil types, three emitter discharges (4, 8, and 12 lph), four slopes (0, 2, 5, and 10%), and five irrigation water volumes (10, 20, 30, 40, and 50 liters) with three replications. The results showed that the surface-wetted area increases as the emitter discharge increases. The surface-wetted area decreased with a corresponding increase in emitter discharge in experimental fields with light-textured soils. In experimental fields with heavy textured soils and slopes greater than 5%, the changes in surface-wetted area due to the emitter discharge increases, were higher compared to slopes of less than 5%. Since, a higher emitter discharge would result in higher surface-wetted area, the results showed that for an equal volume of irrigation water, the soil moisture profile was deeper for lower emitter discharge. In general, the volume of wetted zone was higher for greater emitter discharges. It was found that as the volume of irrigation water increased, the volume of wetted zone would increase correspondingly. This effect is more prominent than that of emitter discharge. In general, the depth of wetting front was lower and the wetted surface area was greater for heavy textured soils as compared to the light textured soils. The wetted-surface area and the shape of wetting front in the direction of slope were affected by the soil infiltration, emitter discharge and volume of irrigation water where these effects were more critical in higher sloping lands.
Sayed Farhad Mousavi, Behrouz Mostafazadeh, Shokrollah Absalan,
Volume 2, Issue 4 (1-1999)
Abstract
This study aims to evaluate the present management of border irrigation systems applied to wheat, alfalfa and sugar-beet farms in Boyer-Ahmad and Gachsaran cities in Kohgiloyeh and Boyer-Ahmad Province. Experimental farms included 8 alfalfa farms, 5 wheat farms and 5 sugar-beet farms. The experiments were conducted at different growth stages of plants and customary borders with prevalent dimensions, slopes, and management practices. The relationship between management allowable deficit, moisture deficit before irrigation, and infiltrated depth indicated that in most cases either “deficit irrigation” or “stress irrigation” had been applied. This type of irrigation has positive effects on water use but negative effects on supply of required soil moisture for plants. In the first to third irrigations, measured application efficiencies ranged from 40.8% to 100%, 52.2% to 100%, and 61.1% to 100%, respectively. Graphs of advance, recession, and ideal recession showed the effects of border slope and length on inflow cut time and uniformity of water distribution. Water infiltration curves showed the amount of deficit irrigation. The results showed that weak irrigation management is the result of three parameters: lack of knowledge on the part of farmers about soil moisture conditions and correct time for irrigation, weak irrigation scheduling, as well as an imbalance between available water supply and irrigation requirements which leads to wasting water and reduced irrigation efficiency.
T. Sohrabi, U.a. Khoshkhahesh,
Volume 3, Issue 4 (1-2000)
Abstract
The purpose of this research is to determine the application efficiency of rice irrigation plots and to analyze the reasons for low efficiency. The study will also try to determine the effective factors which could increase the application efficiency of rice fields. The selection of rice fields was based on climate, soil characteristics, and farmer management. Water application efficiency was determined by field measurements in three modern irrigation networks named Fouman (F), Rasht (G) and Lahidjan (D). In the meantime, a traditional network was included for comparison. In the study areas, the soil texture was heavy with an infiltration rate of less than 3 mm/day. The study was carried out under two different conditions: (1) without return flow and (2) with return flow. In the first case, the average application efficiencies in Fouman (F), Rasht (G) and Lahidjan (D) were about 51.2, 49.0 and 49.4 percent, respectively and the maximum and minimum values were about ((52.6, 49.7)), ((50.7 , 47.3)), and ((50.7 , 48.0)) percent, respectively. In the second case, the average application efficiencies for the above-mentioned regions increased to 73.4, 73.3 and 72.4 percent, respectively and the maximum and minimum values were about ((74.3, 72.4)), ((74.3, 72.1)), and ((73.0, 71.5)) percent, respectively. Runoff ratios in the above-mentioned regions were 30, 33 and 31 percent, respectively. During growing period (from transplanting to harvesting), the average applied irrigation water was about 1130 mm (11300 m3/ha) and the average evapotranspiration was determined to he about 561mm.
M. Mahlooji, S.f. Mousavi, M. Karimi,
Volume 4, Issue 1 (4-2000)
Abstract
A study was conducted to determine irrigation scheduling of pinto bean and to evaluate the effect of its planting date. A split-plot with complete randomized block design with four replications was used at Isfahan University of Technology Research Station in Shervedan-Falavarjan, The main plots were three irrigation regimes of T1 to T3 (irrigation after 50±3, 70±3 and 90±3 mm evaporation from class A pan, respectively) and the sub-plots were two planting dates of May 28 and June 28.
The results showed that delayed planting from May to June caused earlier flowering, physiological maturity and reduction of 29.6% in grain yield. Grain yield in T1 to T3 treatments were 3585.1, 3510.5 and 1925.8 kg/ha, respectively. The difference between grain yields of T1 and T2 with T3 treatments were significant at 1% probability level. Biological yields at May 28 and June 28 planting dates were 8257.1 and 5535 kg/ha, respectively, which were significantly different. There was no significant difference between biological yields of T1 and T2 treatments. Number of pods per square meter was the most important component of grain yield and 85% of grain yield difference was due to this part. Harvest index was affected by irrigation treatment and planting date. Mean harvest indices for T1 to T3 treatments were 45.5, 46.1 and 37%, respectively, and 42.8% and 44.9% for the two planting dates. Water use efficiencies for grain yield in T1 to T3 treatments were 0.557, 0.556 and 0.329 kg/m3, respectively. Generally, treatment T2 was shown to be the best irrigation regime.
A. Hassanli, A. Sepaskhah,
Volume 4, Issue 2 (7-2000)
Abstract
In this study, seven citrus gardens in different parts of Darab were chosen to evaluate the drip irrigation systems. The evaluation process was based on the Merriam and Keller’s model (1978). Besides the evaluation of drip irrigation systems, the water requirement of citrus was estimated using four models including Blany-Criddle modified by FAO, Hargrive-Samani, Pan Evaporation and Solomon-Kodama model. On the basis of the results obtained by Hargrive-Samani with 1296 mm annual water requirements, a comparison was made between irrigation with existing systems and irrigation under favorable and desired conditions.
The results from field measurements indicate a considerable reduction in the emitter discharges. The low pressure and emitter clogging could be two major reasons for the problem. Low pressure at head control, topography, head losses and also using no filter(s) or unefficient filters are the main reasons for the reduction. In some gardens, overirrigation even up to 2.5 times of water requirement was practiced by using extra emitters and increased irrigation times. Overirrigation causes considerable water losses through deep percolation and in reased overwetting area.
Field measurements indicated a good emission uniformity (EU) for the fields with overirrigation. EU in chosen fields varied from 40 to 91%, AELQ varied from 31 to 82% (poor to good) and PELQ varied from 36 to 82%. This study showed that most farmers are not familiar with plant water requirements. The fields with efficient filtration due to using extra emitters per plant are mainly overirrigated. But fields without any filter of unefficient filters are not irrigated sufficiently. The very high manufacturing variation coefficient of IEM emitters (Cv=0.22), which are widely used in Darab, causes a design emission uniformity of 55%.
B. Mostafazadeh, M. Farzamnia,
Volume 4, Issue 3 (10-2000)
Abstract
In this research, the hydraulic behavior of furrow irrigation was investigated under cut-back, Walker-Skogerboe and conventional methods at the three experimental farms of Lavark, Shervedan, and Isfahan University of Technology for three irrigation events. In each farm, data were collected for each of the above methods with at least three replications including furrow shape, furrow length, furrow slope, soil texture, advance and furrow inflow and outflow.
The parameters of Kostiakov-Lewis infiltration function were determined using the volume balance method. The deep percolation ratio, runoff ratio and application efficiency were then computed.
The results showed that deep percolation ratio was higher in the cut-back method as compared to the Walker-Skogerboe method (18.6% as compared to 13.7%) and the runoff ratio was less in the cut-back method as compared to those in the Walker-Skogerboe and conventional methods (12.4% as compared to 16 and 20.6%, respectively). The effect of the two parameters of deep percolation ratio and runoff ratio caused, in general, the application efficiency to be less in the conventional method than those in the cut-back and Walker-Skogerboe methods (42.7% as compared to 69 and 70%, respectively). In general, the cut-back method had a higher application efficiency in heavy texture soils as compared to light texture soils (73.9% as compared to 51.2%).
A. Alizadeh, A.g. Ghorbani, G.h. Haghnia,
Volume 4, Issue 4 (1-2001)
Abstract
In order to compare the effect of drip and furrow irrigation methods with different quantities of water (50%, 75%, and 100% of the amount of water evaporated from class A pan evaporation during irrigation intervals) on yield and quality of tomato, an experiment was conducted on a silty loam soil in Mashhad Agricultural Research Station. The experimental design was a factorial trial with completely randomized blocks and. four replications.
The results showed that the highest yield (51 t/ha) was obtained from the treatment of drip irrigation with 100% water application. This amount was 4.5 tons higher than the yield from furrow irrigation treatment. Deficit irrigation by 25 and 50 percent decreased total yield by 34.7% and 67.95% in the drip irrigation method and by 27.57% and 64.29% in the furrow irrigation, respectively. Water use efficiency in drip irrigation was two times higher than that in the furrow treatment. Quality and chemical composition of the fruits were not significantly different in the two irrigation methods. Increasing the water deficit, however, increased the amount of soluble solids of the fruits.
S.h. Zand-Parsa, Gh.r. Soltani, A.r. Sepaskhah,
Volume 5, Issue 3 (10-2001)
Abstract
In this study, the optimum irrigation depths for corn grain production under different conditions, i.e. maximum grain yield production and maximum benefit under limited land and water conditions, were determined under sprinkler irrigation in Bajgah (15 km. north of Shiraz).
The results showed that, the optimum depth of irrigation for maximum grain yield production was 77.0 cm. Because of low price of irrigation water and sensitivity of corn crop to water deficit, the optimum depths of water were 76.8 and 73.4 cm under land and water limitations, respectively. Therefore, under limited water conditions, only 4.7 percent of the full irrigation water (maximum corn grain production) can be saved for maximum profits.
A. Erfani, G.h. Haghnia, A. Alizadeh,
Volume 6, Issue 1 (4-2002)
Abstract
A field study was conducted at the College of Agriculture, Ferdowsi University of Mashhad, to investigate the effect of irrigation with treated municipal wastewater on the yield and quality of lettuce and some soil characteristics. Five irrigation treatments were applied to a clay loam soil, classified as fine loamy mixed mesic Calcixerollic Xerochrepts, in a randomized block design with 5 replications. The treatments consisted of T1 (Irrigation with treated wastewater over all growing season), T2 (Alternate irrigation with treated wastewater and well water), T3 (Irrigation with well water and application of cattle manure), T4 (Irrigation with well water plus fertilizer N and P), and T5 (Irrigation with well water only as control). Chemical analysis of well water proved to be a suitable source for agriculture.
The results showed that the yield was higher in T1, T2, T3 and T4 as compared to the control treatment. Maximum fresh and dry yields were obtained from T3 & T1 and T1 & T3, respectively. Plant tissue analysis showed an increase in macronutrients (N, P, K) and heavy metal concentrations in shoots and roots of lettuce in the first four treatments as compared to the control. In T1, iron concentration was maximum while that of cadmium was minimum. Furthermore, microbial contamination was considerably higher in T1 and T2. Soil analysis indicated that in plots treated with wastewater, electrical conductivity, total nitrogen, available phosphorus, soluble boron and heavy metal concentration increased. However, their values were all below international standards. More experiments seem to be necessary in this regard.
B. Mostafazadeh, M. Kahnouji,
Volume 6, Issue 1 (4-2002)
Abstract
The emitter discharge is affected by parameters such as pressure, irrigation water temperature, manufacturer’s coefficient of variation, and emitter clogging. In order to study the effects of irrigation water temperature on emitter discharge and to determine the discharge-pressure variations and manufacturer’s coefficient of variations, an experimental trickle irrigation system was designed and studied in the greenhouse, College of Agriculture, Isfahan University of Technology. Since the sensitivity of different emitters to water temperature variations is variable, four different, widely used, types of Iranian emitters including in-line long-path emitter, gun emitter, pressure compensating emitter, and double-chamber tube were used. Each emitter was evaluated under 14 different irrigation water temperature treatments ranging from 11 to 43.5°C.
The results showed that in general as water temperature increases, the emitter discharge increases linearly in all types, except for the pressure compensating emitter in which the discharge decreases linearly. The emitter uniformity, absolute emission uniformity and Christiansen uniformity coefficient parameters were affected by emitter discharge variations. For each type of emitter under study, the changes in manufacturer’s coefficient of variations due to irrigation water temperature were different. The manufacturer’s coefficients of variations at a water temperature of about 20°C for double-chamber tube, in-line long-path emitter, gun emitter and pressure compensating emitter were equal to 5, 7, 13 and 22 percent, respectively. Moving from gun emitter to the double-chamber tube and finally to the in-line long-path emitter, the sensitivity to irrigation water temperature decreased. Sensitivity to pressure variations decreased in the order of gun emitter, double-chamber tube, in-line long-path emitter, and finally pressure compensating emitter.
M. J. Monem, M. R. Alirezaee, E. Salehi,
Volume 6, Issue 4 (1-2003)
Abstract
Recent studies have shown poor performance of irrigation systems, which indicates the requirement for special attention to performance improvement. The first step for improving the performance of irrigation systems is evaluation of the present situation. Performance evaluation methodologies presented so far are either qualitative such as DA (Diagnostic Analysis), RA (Rapid Appraisal) and FA (Framework Appraisal), or they are similar to classical methods even if they produce quantitative indicators. They fail to introduce performance standards. In this study, using Data Envelopment Analysis (DEA), which is a quantitative method and produces realistic standards, 8 irrigation systems were evaluated and their performances were determined. With respect to the number of decision-making units, inputs, outputs, and corresponding returns to scale for irrigation systems, a suitable DEA model was selected. Capabilities of DEA allow for separate treatment of performance evaluation of overall irrigation network and its operating company. This feature is implemented using different technical and operational indicators.
The results indicated that Zayandeh Rood irrigation system, among the 8 irrigation systems, has the highest technical efficiency. Minab and Varamin systems have the lowest technical efficiencies. Golestan and Behbahan Networks perform well, although their operating companies are inefficient. Garmsar, Ghazvin, and Moghan systems, although not inefficient, have some improvement potentials. In general, with respect to the capabilities of DEA in performance evaluation of irrigation systems and indicating appropriate standard, it can be concluded that this technique is quite efficient and successful for performance evaluation and improvement of irrigation systems.
M. M. Ghasemi, A. R. Sepaskhah,
Volume 7, Issue 2 (7-2003)
Abstract
In this study, the effect of deficit irrigation with every–other furrow irrigation method, which is an innovated method in farm irrigation management, was examined on sorghum (Sorghum durra L.) in Bajgah and Kooshkak areas of Fars Province. The experimental design was split plot with three main plots of irrigation interval (10, 15 and 20 days), three subplots of irrigation methods (ordinary furrow, fixed and variable every–other furrow), and 4 replications. Considering the crop production cost with real and subsidized prices of water in both areas, the net benefit per unit volume of irrigation water and benefit–cost ratio were calculated. The results showed that these economic parameters for the fixed and alternative furrow irrigation methods of 10-day intervals in both areas did not differ much with those of the ordinary furrow irrigation with 10-day intervals and were even higher in Bajgah area. Furthermore, the relationship between the amount of irrigation water, water application efficiency (Ea), water price per unit volume (Cw) and the net benefit per unit volume of irrigation water (B) with different conveyance efficiencies (Ec) were determined by multiple linear regression procedure. The regression coefficients of linear fit equation between the costs and irrigation water were determined. The results indicated that with higher price of water, the farmer should increase the farm irrigation application efficiency to avoid the economic losses.
J. Abedi Koupai, M. A. Fathi,
Volume 7, Issue 2 (7-2003)
Abstract
Rice husk, an agricultural waste, is produced about 100 million tons annually in the world and 0.5 million tons in Iran. Due to growing environmental concerns about disposal of these wastes, efforts are required to apply the wastes in industry. In this research, the mechanical properties of concrete incorporating rice husk ash (RHA) in sulfate environments (such as irrigation canals) were investigated and the increase in concrete strength was compared with control samples. In order to burn the husks at a controlled temperature to obtain a highly reactive pozzolanic RHA, a furnace was designed and built. The experiments included 405 samples of cubical (707070-mm) and cylindrical (50.8101.6-mm) concrete samples (105 samples for A, B and C treatments, respectively) which were stored in different ages (7, 28, 60, 180 days) under three different conditions (solutions of magnesium, calcium and sodium sulfates). The portions of RHA as cement replacement were 20 and 30 percents for B and C treatments.
The results showed that the samples of concrete containing 20 percent RHA as cement replacement had higher compressive and tensile strengths in sulfate environments at 180 days compared with those of control concretes. The concrete samples containing RHA showed sharper gradients compared to control samples of up to 180 days under sulfate conditions. The best portion of RHA in concrete was determined to be 20 percent by weight.
A. F. Mirlohi, M. H. Ehtemam, M. R. Sabzalian,
Volume 8, Issue 2 (7-2004)
Abstract
A major limitation for higher yield of rice plant is water availability. Water use efficient varieties tolerant to upland conditions could help to relax this limitation. Three separate experiments were conducted to study the effects of water regimes on growth, aerenchyma formation, and nutrient absorption of Iranian rice varieties. In the first experiment, five varieties of rice were grown under three different irrigation levels. The second experiment involved the study of nutrient uptake by Sazandagee and Tarom varieties under four different water regimes, and in the third experiment, the effect of aeration on growth characteristics of Sazandagee rice was assessed in a hydroponics system.
Results of the first experiment showed that submerged conditions continuously or after four weeks of initial growth had a significant effect on plant growth. Aerenchyma formation was affected by rice varieties and was less affected by irrigation status. In the second experiment, plant growth characteristics were affected similar to experiment one. Also it was shown that nutrients such as P, Mg, and Fe were absorbed with higher efficiency under submerged conditions. Results of the third experiment revealed that aeration had no significant effect on plant growth characteristics. Based on the results of these three experiments, it can be concluded that better performance of rice plant under continuous or partial flooding is mainly related to higher absorption of some macro - and micronutrients. Therefore, this parameter should be considered in water management programs for rice.
J. Abedi Koupai, A. Bakhtiarifar,
Volume 8, Issue 3 (10-2004)
Abstract
Water crisis is an important issue in arid and semi-arid regions like Iran. The situation has been getting more worse over recent years drought. Hence, there is a growing need to utilize low quality water where freshwater is scarce. In this regard, urban wastewater is a promising source but there are concerns about the environmental and health aspects of using such water. The main problem regarding the performance of trickle irrigation system utilizing wastewater effluents is clogging of the emitters. In this study, field trials at pilot scale were carried out to investigate the hydraulic properties of emitters using two types of water including treated wastewater and groundwater. The trickle irrigation system consisted of three 16 mm lateral tubes placed at 300 mm spacing in the main tube and each lateral tube had 16 emitters at 300-mm spacing. The designed discharge of the emitters was 4 L/h. The hydraulic properties of the different commercial emitters (micro flapper, long path, turbo plus and Eurokey) were assessed at different time periods.
The results indicated that the Eurokey and long path emitters had the maximum and minimum emission uniformity, respectively, when applying wastewater. using groundwater, the Eurokey and turbo plus emitters had the maximum and minimum emission uniformity, respectively, during the initial phase of the study. However, the Eurokey and long path emitters had the maximum and minimum uniformity values, respectively, at the end of the study. The turbo plus emitters are regulated and, as a result, showed no evidence of sensitivity to pressure variations hence, they can be used on uneven lands and where the trickle irrigation system has long lateral tubes.
A. Montazar, S. Kouchakzadeh, A. Liaghat, M. H. Omid,
Volume 8, Issue 3 (10-2004)
Abstract
The operation of an irrigation network is the result of a decision-making system in which three elements, i. e. the physical condition of the structures, control capacity, and hydraulic behavior of canal system, have important roles. The impact of these components is incorporated in the hydraulic sensitivity concept. For this purpose, the sensitivity of structures could be considered as the most important factor in the hydraulic characteristics of a system. The sensitivity analysis approach is one of the flow analysis methods that is used to forecast the flow behavior in several irrigation networks. Baffle Modules are one of the most suitable structures for flow regulating and delivery. In this paper, hydraulic sensitivity equations are presented for this type of structure. Also, the quantitative variations of the sensitivity index have been evaluated under operating conditions and compared with those of theoretical conditions. Then the influence of the sensitivity index variations on the performance of structures has been studied. This study was carried out on some modules of the Qazvin network.
The results indicated that the hydraulic sensitivity of these off-takes varies under operating conditions. In some cases, variations were estimated to be more than 100%. The range of discharge variations was twice the predefined acceptable value (20%) in some offtakes.
F. Foroughi, A. A. Ghaemi,
Volume 9, Issue 2 (7-2005)
Abstract
In irrigation scheduling, one question is “how much is the optimal depth?”. In this study the optimal irrigation depth (by assuming the power distribution function and by taking into consideration the distribution function, which governs the data (normal distribution)) by considering the environmental effects was determined for three water management strategies (i. e. unlimited, limited nitrogen leaching and environmental protection) for wheat under center pivot irrigation system. The System layout in 32 hectare field was installed according to the ASAE standard. Four radial lines of catch cans were used at intervals of 6m (two radial lines of catch cans A and B, were installed on the maximum slope with 3˚ between every two rows and two radial lines of catch cans C and D, were installed on the minimum slope with 3˚ between every two rows). The field data were collected by the five different speeds of the center pivot system. The economical ratio (C) for three water management strategies were 31.19, 4.58 and 1.45, respectively. The optimum irrigation water was calculated for the three different management strategies.
The results indicated that the lowest value of optimal irrigation depth was observed under the unlimited strategy, and the highest value of optimal irrigation depth was found for the environmental protection strategies (both with assuming power distribution and normal distiribution function).
