Iranian Journal of Irrigation and Drainage
Year:2008 | Volume:2 | Issue:1|Papers Count:13

Contaminated soils and waters with heavy metals pose a major environmental and human health problem that needs an effective and affordable technological solution. Heavy metals are the most common contaminants at hazardous waste sites. Among heavy metals, lead (Pb) and cadmium (Cd) are the most common contaminants, posing serious and sometimes life threatening health hazards. Phytoremediation is a safe technology that employs plants to remediate contaminated soils. This technology, compares to those that involve the use of large scale energy consuming equipments, is an inexpensive method. The effectiveness of this new technology is needed to be demonstrated by means of mathematical modeling. A thorough literature review indicates that very few models have yet been developed for phytoextraction due to complexities involved within the soil-chemicals-water-plant system. The objective of this study was to develop a simple model for phytoremediation of Pb- and Cd-polluted soils. A new formulation of phytoremediation was established based on soil and plant responses to Cd and Pb pollutants. This approach assumes that the relative transpiration reduction can resemble the total Cd and Pb concentrations in the soil. Combining the related functions of soil and plant responses to soil Cd and Pb concentration, the phytoextraction rate of Cd and Pb were predicted. To verify the mathematical derivations, an extensive experimental set up was established to obtain the needed data. Consequently, large quantity of a sandy loam soil was thoroughly mixed with Cd and Pb to obtain homogeneous concentration of these pollutants within the soil matrix. The contaminated soils were then carefully packed into the designated pots. Land Cress (Barbarea verna) and Spinach (Spinacia oleracea L.) seeds were germinated in the pots containing 8 kg of contaminated soil. The total concentrations of Pb and Cd in the soil and plant samples were extracted by 4M HNO3 digestion and wet oxidation methods, respectively. The water-soluble fraction of soil Pb and Cd were then obtained by leaching with distilled water for 24 h at 1:2 soil-liquid ratios and measured with flame and graphite furnace atomic absorption spectrometry instruments. Combining the relative transpiration rate models with the plant concentration models, also indicated a reasonable performance for both Pb (R2> 0.89) and Cd (R2 = 0.83) pollutants.

Improvement of irrigation network operation calls for identifying the unsteady flow characteristics and determining its influences on the operation process. Wave generation and propagation because of normal structure operations are very common phenomena in irrigation networks. Along a channel reach the characteristics, i.e. shape and height, of the transmitted wave change during its movement, which are usually considered one dimensional flow and determined by solving the Saint Venant equations. However, the Froude number in the irrigation canals is usually small enough to drop the inertia terms from the dynamic equation to yield diffusive wave model which could effectively be used in determining the flow behavior within the canal. In this research based on the solution of diffusive wave model, analytical relationships were developed to determine the travel and response times of a wave generated by an abrupt discharge change in the upstream side of a channel reach. The outputs of the proposed relationships were compared with that of a full hydrodynamic model which illustrated the validity and effectiveness of the proposed method. The relationships of travel And response times were, then, employed for determining the operational losses in irrigation canal to present their validity and usefulness for network management.

Scarcity of water resources and growing competition for water will reduce its availability for irrigation. At the same time, the need to meet the growing demand for food will require increased crop production from less water. Deficit irrigation is one way of maximizing WUE and WUEI for higher yields per unit of irrigation water applied. This study was conducted to evaluate the effects of deficit irrigation on yield and yield components of sugar beet and WUE and WP. The study was carried out, using split-plot design on base of randomized complete blocks with 3 irrigation treatments of levels of irrigation (100%, 75% and 50%), 3 treatment of intervals (7,10,14 days) in 4 replications in Meandoab Agricultural Research station in production season 1999-2000.there was a significant difference (1% significant level) among deficit irrigation and interval irrigation on root yield and the sugar yield. The highest root yield and sugar yield were obtained by D7I100 treatments, 67.7 and 10.2 t/ha respectively, with 797mm of Et. 25% and 50% deficit irrigation caused decreasing of root yield, 13.3% and 33.3% respectively, and sugar yield, 11.1% and 28.9% respectively, with 77.5% and 55.8% water applied by full irrigation (I100) treatment. Increasing interval from 7 to 10 and 14 day caused decreasing of root yield by 3.5% and 8.6% and water used by 8.0% and 17.0%. In full irrigation (I100), 175 and 150 treatments, WUE was 8.4, 9.7 and 11.2 kg.ha-1 respectively. Considering water productivity and irrigation management, D10175 treatment recommended in the region. In this treatment, with 29.0% saving of water irrigation, the root yield and sugar yield only decreased 23.0% and 17.1% respectively in compared with D7I100 treatment. The crop response factor (ky) was determined as 0.712 and 0.823 for 2 years. The root yield increased as the applied irrigation water increased, and a linear relationship was found between these 2 parameters.

The irrigation management and water productivity of four irrigation district in Esfahan was evaluated by using remote sensing data and various irrigation management indicators such as volume of water supply and demand, relative water supply, water productivity and economic water productivity. In order to obtain the required data, it was attempted to upscale the accuracy of NOAA satellite images by using Landsat images. From a time series of NOAA images during the one growing season, NDVI, SAVI and LAI indicators were established. Based on these indicators the actual irrigated area was evaluated for each irrigation systems in the Zayandeh Rud basin. The actual water use for each irrigation district was estimated by actual evapotranspiration from a time series of remote sensing data during the growing season. NOAA satellite images were analyzed using the SEBAL (Surface Energy Balance Algorithm for Land) algorithm to obtain actual and potential evapotranspiration and biomass production. The assessment of the irrigation systems was expressed based on Productivity of Water, defined as Kg biomass over m3 evaporated water. Results indicated the same trend for biomass production, NDVI and ETact levels in the all irrigation systems, where high biomass values correspond to high NDVI and ETact. The peaks of biomass production values happened in May when climatic conditions in terms of radiation are optimal and sufficient water is available from precipitation, soil moisture storage, and irrigation. The overall water balances for the systems were not closed and three of the four systems show a water deficit. The other water used in the three water deficit irrigation systems can be supplied from other water resources, which is not included in the water balance. The average water productivity for all of the crops during the growing season was between 0.7-0.9 kg/m3.

About 23.4 million hectares of arable land in Iran have salinity problems due to the Sodium and Chloride accumulation in the soil profile, poor drainage, low irrigation water quality and incorrect irrigation system. Trees faces with sever growth reduction, pre-time leave shed, leave edge necrosis, nullness of fruits and product reduction due to weak drainage of soil. Irrigation water characteristics: EC=4.26 dS.m-1 pH=7.34, SAR=9.39, Na+ =21, Cl-=25 and HCO3- =1.6 (meq.lit-1).The main purpose of this research is to study the effect of applied reclamation methods on improvement of soil physical and chemical properties in a 50 hectares saline and sodic soils of pistachio in 0-35 cm depth with loam-clay loam texture in Garmsar region. The experiment was done in split plot statistical arrangement based on the randomized blocks with 4 treatments in three replicates: T0 evidence (soil before additions), T1 (leaching+ drainage) , T2 (T1+sulfur), T3(T2+deep plow+ animal manure), statistical analysis were done using MSTATC software. The results have shown that treatment T3 (P£0.01) had the highest effect on the reduction of salt concentration at soil surface layers so that Na+, cr changed from 81 and 110 to 6.33 and 13 (meq.lit-1) respectively, bulk density from 1.45 to 1.3 (g.cm-3) hydraulic conductivity from 5 to 55 (mm.h-1), pH from 8.2 to 7.7, ECe from 8.9 to 4.36 (dS.m-1), SAR from. 19.8 to 3.38 and ESP from 21.96 to 3.58 which is consequence of drainage and leaching. The results of leave analysis after three years experiment have shown that N, P, K. Fe, Cu, Zn, Mn concentrations have increased, adding enough organic mater and deep plowing which causes higher soil permeability and porosity and better water and element absorption in roots. Soil reclamation causes improvement in its physical and chemical properties which causes increase in growth of trees and higher production.

Improvement of water use in agriculture is considered the highest among other water users because of complications in consumption and production process. Determination of water potential with considering its inter-relationships with the soil, plant and atmosphere and the value of water productivity can be used as the proper index in evaluation the state of water use. Determination of different yield levels through field experiments is difficult for various temporal and spatial ranges. Therefore, applying simulation models could be a method which makes it possible to assess water balance, simulate growth process and study different scenarios. For that, combination of Geographic Information Systems (GIS) and crop models is necessary. The objective of this study is to apply CropSyst crop growth model coupled with GIS to analyze water productivity, which is an indicator of water use efficiency at the basin. Hence, Karkheh river basin in west of Iran was selected and zoning of water productivity was done basis of calculations and analysis. The simulations were done in dry and potential yield levels for wheat crop. For investigating temporal variations of water productivity in continuous record periods, this index was analyzed in three conditions drought, wet and normal years by use of Standard Precipitation Index (SPI) in basin and prepared ifs spatial extension maps. The results showed that water productivity and potential production of wheat in drought condition were highest among the wet and normal conditions because of higher solar radiation value through growing period. In, this situation, the maximum of water productivity is 0.62 kg/m3 that highest it's spatial extension is in north and northwest of watershed. In wet condition, northeast and east of region have the maximum of water productivity of 0.53 kg/m3 and in normal condition, the parts of watershed's east and west have the maximum of water productivity 0.59 kg/m3. Hence, the spatio- temporal analysis of water productivity provides substantial information for water saving opportunities. Also, since those temporal and spatial dimensions could be studied at once, the combination and development of GIS and crop growth model allowed a more effective analysis and broader understanding about the implications of the indices under investigation.

Limitation in water resources caused that agricultural sector, the main water user in the country, to be faced a serious water deficit for food production. Herein, the main challenge of agricultural sector is improvement of water productivity and more food production using less water. In agricultural production systems, water use efficiency (WUE) accounts for crop production per unit amount of water used. This study was aimed to (i) determine wheat and maize water productivity under full irrigation, (ii) evaluate the impact of deficit irrigation on WUE, and (iii) improve WUE considering regional relative advantages in cropping pattern system. Based on the experiments conducted in north regions of the country (Karaj, Mashhad, and Orumieh) during 1998-2003, it was found that the range of wheat and maize WUE was 0.4-1.3 and 0.8- 2.3 kg m-3 which was wider than that reported earlier by the FAD, 0.8-1.0 and 0.8-1.6kg m-3, respectively. The wide ranges of WUE indicate tremendous opportunities for increasing the agricultural productions with less water. The maximum measured wheat and maize WUE was 1.73 and 2.63 kg m-3 from Karaj and Urmieh, respectively, when deficit irrigation management was applied. Wheat and maize WP of 1.0 and 1.3kg m-3 were recommended as optimum level to be considered in cropping system of potential regions. Water applied (irrigation and effective rainfall) for optimum level of wheat and maize WP was 400 and 600mm, respectively.

The aim of this paper is develop a non-linear optimisation model for the determination of the optimised water allocation and cropping pattern based on crop water production functions and irrigation uniformity. The proposed model was applied for Qazvin Irrigation Network. The results showed that among the crop types grown in the region, onion and alfalfa have the highest and the lowest water productivity value, respectively. These values under drought conditions for optimal cropping pattern of the two crops were estimated at 75069 and 3055 Rls/m3.The results showed that the greatest cultivated areas belonged to wheat which were 23599 and 19350 ha for wet and dry years, respectively. The findings indicated that the overall water productivity of the irrigation network with relevant cropping pattern management may be rised to as high as 12665 Rls/m3 under drought condition. The results demonstrated that the water productivity of irrigation network can be improved as result of optimal cropping pattern and deficit irrigation. The maximum variations of this indice may be fixed around 1.7 % for different water regimes as a result of the optimized water allocation and cropping patten. The proposed model may be used to optimize the global water productivity of the irrigation networks. Hence, it can be had an important role into improving irrigation systems efficiency and managing water in a sustainable manner.

Generally speaking, the aims of the agricultural planners and decision makers may be much beyond the interests of the ordinary farmers. Farmers are usually seeking maximum benefits in a year or so without considering environmental problems, ground water depletion or the sustainability of resources. In the other hand the planners aims are the sustainability of water and land resources, as well as the environmental conservation and agricultural job security. In this study a fuzzy goal programming (FGP) was developed while the above mentioned goals have been considered. Fariman- Torbatjam agricultural plain in Khorasan razavi has been used as a case for implementing the results of the re4search. The model is able to maximize each of the goals or optimizing the counter goals. The results showed that it is possible to save groundwater resources and benefits of the farmers in a period of 10 years.

Agricultural water demand is the major source of water consumption in Iran. The modification of conventional irrigation methods and development of modem techniques will result in an increase in water use efficiency. Drip-tape irrigation is one of the newly developed methods, being extended over the country. This study was conducted to investigate the hydraulic properties of the pipes used in drip tape irrigation. The main hydraulic properties of these pipes such as dripper discharge and its variation along the pipes by the initial pressure, variation of drippers discharge along the pipe and pressure drop for different pipe lengths has been studied based on the gradually varied flow conditions.