Actual Irrigation Research Articles

A Bayesian assessment of the current irrigation water supplies capacity under projected droughts for the 2030s in China

Crop models often simulate drought impacts with full and no irrigation scenarios, while planners are more interested in whether the current available irrigation water can cope with the future more serious droughts. This paper addresses a key constraint common to modeling studies: the limited representation of actual irrigation water supply. We present a data-driven approach to identify a benchmark for agronomic drought risk levels as defined by water availability thresholds at the baseline climate (1980–2008) using reported crop yields, climate and irrigation statistics. Then, holding the current irrigation supplies, we adopted Bayesian formula to estimate magnitude of the future water availability and the associated probability of crops yields being decreased to rainfall-deficiency under climate conditions in 2030s (2020–2040) based on the RegCM3 climate model output driven by IPCC SRES A1B scenario. Results reveal that future drought stress would overwhelm the irrigation capacity of current supplies in northern and western China, while drought remains at baseline climate levels in the central, eastern and southern regions. The largest increases in the probability of projected drought risk were in northeast and southwest, ranging from 14% to 28% above baseline climate. Regional drought impacts for grain self sufficiency are discussed.

Effect of Wetting-Drying Cycles on Redistribution of Lead in Some Semi-Arid Zone Soils Spiked with a Lead Salt

Mobility and bioavailability of lead (Pb) could be affected considerably by soil physicochemical properties; however, less is known about the effect of Pb levels and aging time. This study was conducted to evaluate the effects of Pb levels and wetting-drying (WD) cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb(NO3)2. Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils. A soil with a long history of Pb contamination was also taken as a reference soil. The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d. Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils. Redistribution index (Uts) and reduced partitioning parameter (IR) were applied to semi-quantify the distribution of Pb in the spiked soils. A small amount of Pb sorbed was desorbed by the soils, indicating a strong and irreversible binding of Pb in the studied soils. Contribution of carbonate-bound (Car) and residual (Res) Pb fractions to the total Pb of the soils was more than 97%. The Car, soluble plus exchangeable (SE), and organic matter-bound (OMB) fractions of Pb were transferred to the Res fraction under the WD cycles. The IR and Uts values were influenced by Pb loading levels and WD; therefore, the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters. At the end of the experiment, the Ir and Uts values for the Pb salt-spiked soils did not show the quasi-equilibrium state. The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition. WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.

Assessment of the Irrigation Advisory Services’ Recommendations and Farmers’ Irrigation Management: A Case Study in Southern Spain

The Local Irrigation Advisory Services (LIAS) carry out essential work to achieve an efficient use of irrigation water at field and irrigation scheme level, which is crucial in Mediterranean irrigation systems. However, it is unusual to find agronomic and economic assessments of LIAS advice. In this work, the LIAS operating in the Genil–Cabra Irrigation Scheme (southern Spain) was evaluated during the first 5 years of its advice. Acceptance by farmers of the LIAS recommendations was evaluated by using agronomic indicators, such as ARIS (Annual Relative Irrigation Supply). ARISLIAS (actual irrigation applied v. recommendation of LIAS) with values ranging from about 0.23 for wheat and sunflower, and 0.94 for maize, also detecting a high variability between farmers, which indicated a scant acceptance of the LIAS recommendations. The economic evaluation of irrigation was made through two economic indicators, Irrigation Water Productivity (IWP) and Irrigation Water Benefit (IWB). IWP values varied significantly between different crops: around 0.23 € m−3 in wheat, sunflower and maize, about 0.53 € m−3 in cotton and sugar beet, and values higher than 2.0 € m−3 in garlic, for optimal irrigation schedules. For IWB, trends were similar, emphasizing the low IWB values in wheat and sunflower (average values of 0.06 and 0.13 € m−3, respectively). Consideration of these economic indicators by LIAS could not only help to obtain more suitable and economically profitable irrigation schedules, but also contribute towards a greater acceptance of advisory services by farmers, by shifting the emphasis from maximizing production to maximizing irrigation profitability.

Detecting Critical Points in On-Demand Irrigation Pressurized Networks – A New Methodology

In many pressurized irrigation water distribution networks, rising energy costs are having a significant impact on system performance, environmental impact and the profitability of agribusinesses and farms dependant on water supplies for irrigated production. In this study, a new methodology is proposed for analysing the location of critical control points (hydrants) to reduce energy consumption. The methodology is developed and applied using two irrigation districts located in Southern Spain (Fuente Palmera and El Villar). The new approaches provide a framework for comparing different energy saving strategies, including improved critical point management and network sectoring. The results show that potential energy savings of around 10% and 30% are possible in each district when the theoretical irrigation requirements are modeled. However these savings reduce to 5% and 12% when the local farmers’ practices of deficit irrigation are incorporated. These results are compared to those obtained for networks sectoring in the same irrigation networks in a previous work. The study confirms that that a sectoring approach works best for reducing the energy costs associated with meeting actual irrigation water demands in irrigation districts where energy consumption is a limiting factor on production.

Irrigation and Autocracy

We show that societies with a history of irrigation-based agriculture have been less likely to adopt democracy than societies with a history of rain fed agriculture. Rather than actual irrigation, the empirical analysis is based on how much irrigation potentially can increase yields. Irrigation potential is derived from a range of exogenous geographic factors, and reverse causality is therefore ruled out. Our results hold both at the cross-country level, and at the subnational level in premodern societies surveyed by ethnographers.

The blue, green and grey water footprint of rice from production and consumption perspectives

The paper makes a global assessment of the green, blue and grey water footprint of rice, using a higher spatial resolution and local data on actual irrigation. The national water footprint of rice production and consumption is estimated using international trade and domestic production data. The global water footprint of rice production is 784 km 3/year with an average of 1325 m 3/t which is 48% green, 44% blue, and 8% grey. There is also 1025 m 3/t of percolation in rice production. The ratio of green to blue water varies greatly over time and space. In India, Indonesia, Vietnam, Thailand, Myanmar and the Philippines, the green water fraction is substantially larger than the blue one, whereas in the USA and Pakistan the blue water footprint is 4 times more than the green component. The virtual water flows related to international rice trade was 31 km 3/year. The consumption of rice products in the EU27 is responsible for the annual evaporation of 2279 Mm 3 of water and polluted return flows of 178 Mm 3 around the globe, mainly in India, Thailand, the USA and Pakistan. The water footprint of rice consumption creates relatively low stress on the water resources in India compared to that in the USA and Pakistan.

Irrigation scheduling performance by evapotranspiration-based controllers

Abstract Evapotranspiration-based irrigation controllers, also known as ET controllers, use ET information or estimation to schedule irrigation. Previous research has shown that ET controllers could reduce irrigation as much as 42% when compared to a time-based irrigation schedule. The objective of this study was to determine the capability of three brands of ET-based irrigation controllers to schedule irrigation compared to a theoretically derived soil water balance model based on the Irrigation Association Smart Water Application Technologies (SWAT) protocol to determine the effectiveness of irrigation scheduling. Five treatments were established, T1–T5, replicated four times for a total of twenty field plots in a completely randomized block design. The irrigation treatments were as follows: T1, Weathermatic SL1600 with SLW15 weather monitor; T2, Toro Intelli-sense; T3, ETwater Smart Controller 100; T4, a time-based treatment determined by local recommendations; and T5, a reduced time-based treatment 60% of T4. All treatments utilized rain sensors set at a 6 mm threshold. A daily soil water balance model was used to calculate the theoretical irrigation requirements for comparison with actual irrigation water applied. Calculated in 30-day running totals, irrigation adequacy and scheduling efficiency were used to quantify under- and over-irrigation, respectively. The study period, 25 May 2006 through 27 November 2007, was drier than the historical average with a total of 1326 mm of rainfall compared to 1979 mm for the same historical period. It was found that all treatments applied less irrigation than required for all seasons. Additionally, the ET controllers applied only half of the irrigation calculated for the theoretical requirement for each irrigation event, on average. Irrigation adequacy decreased when the ET controllers were allowed to irrigate any day of the week. All treatments had decreased scheduling efficiency averages in the rainy season with the largest decrease of 29 percentile points with a timer and rain sensor (T4) and an average decrease of 20 percentile points for the ET controllers, indicating that site specific rainfall has a significant effect on scheduling efficiency results. Rainfall did not drastically impact the average irrigation adequacy results. For this study, there were two controller program settings that impacted the results. The first setting was the crop coefficients where specific values were chosen for the location of the study when calculating the theoretical requirement whereas the controllers used default values. The second setting was the soil type that defines the soil water holding capacity of the soil. The ET controllers were able to regularly adjust to real-time weather, unlike the conventional irrigation timers. However, the incorporation of site specific rainfall measurements is extremely important to their success at managing landscape water needs and at a minimum a rain sensor should be used.

Low energy consumption seasonal calendar for sectoring operation in pressurized irrigation networks

Pressurized irrigation networks and organized on-demand are usually constrained by the high amounts of energy required for their operation. In this line, sectoring, where farmers are organized in turns, is one of the most efficient measures to reduce their energy consumption. In this work, a methodology for optimal sectoring is developed. Initially it groups similar hydrants in homogeneous groups according to the distance to the pumping station and their elevation, using cluster analysis techniques and certain dimensionless coordinates. Second, an algorithm based on the EPANET engine is implemented to search for the best monthly sectoring strategy that accomplish supplying the actual irrigation demand under minimum energy consumption conditions. This methodology is applied to two Spanish irrigation districts (Fuente Palmera and El Villar). Results showed that organizing the networks in sectors, annual energy savings of 8 and 5% were achieved for Fuente Palmera and El Villar when the theoretic irrigation needs were considered. However, these savings rose up to 27 and 9%, respectively when the local practices, deficit irrigation, were taken into account. Thus, they confirm that water and energy efficiency cannot be optimized independently and need to be considered together.

Estimating actual irrigation application by remotely sensed evapotranspiration observations

Water managers and policy makers need accurate estimates of real (actual) irrigation applications for effective monitoring of irrigation and efficient irrigation management. However, this information is not readily available at field level for larger irrigation areas. An innovative inverse modeling approach was tested for a field in an irrigation scheme in southern Spain where observed actual evapotranspiration by satellites was used to assess irrigation application amounts. The actual evapotranspiration was used as the basis for an optimization procedure using the physical based SWAP model and the parameter optimization tool PEST. To evaluate the proposed techniques two steps were taken. First, actual observed evapotranspiration from remote sensing was used to optimize two parameters of the SWAP model to determine irrigation applications. Second, a forward–backward approach was applied to test the minimum overpass return time of satellites and the required accuracy of remotely sensed actual evapotranspiration for accurate assessment of irrigation applications. Results indicate that irrigation application amounts can be estimated reasonably accurately, providing data are available at an interval of 15 days or shorter and the accuracy of the signal is 90% or higher.

Management and evaluation of withdrawal ground water for agriculture in hamdan directorate-Yemen

The aim of this research was to evaluate and determine ground water withdrawal for agriculture in hamdan directorate. The research was done by using random sample to measure and read the requirements data of agricultural hamdan wells. Associate professor, Agric. Eng. Depart., Fac. of Agric, Sana'a Univ. Yemen. abdallayaya87@yahoo.com Annual ground water withdrawals were compared with both of annual renewable ground water and actual crops water requirement in hamdan. Actual crops water requirements and irrigation scheduling, and quantity of water to be applied using surface and drip irrigation systems were done depending on data each of hamdan climate, crop coefficients and soil type by using a computer program (FAO). The results showed – as sample:- In hamdan directorate, the volume of annual groundwater recharge was found 3.341 MCM per year, while annual withdrawals volume of groundwater from all agricultural wells was found more than 99 MCM per year for irrigating only 5737ha. Thereby annual withdrawals of ground water was exceeded the renewable ground water by 29 times, So annual decrease of ground water level was found 3.4 m/year. About 90% of wells were not increased the distance among them on 500m. The distance average among wells in all directions was found 710m. The average of ground water amount for each hectare in hamdan was found more than 2.5 twice and twice of the actual water irrigation requirement for both of drip and surface irrigation systems respectively. So if drip irrigation system will be used in hamdan, it can be kept 47 MCM per year, which is now nearly 50% of withdrawal ground water. The time period of irrigation was found three times of calculated actual irrigation period average. Amount of irrigation water was found more with 7% and 38% than calculated actual amount average of irrigation water for each of surface irrigation and drip irrigation system respectively. The result was indicated that pump power was found excrescence on request (lost) with 54 KW/pump, so there was run-over power equal more than 900 pumps with power 43 KW, which can be provided from hamdan's pumps. Also, motor's power was found excrescence on request (lost) with 40 KW/motor, so there was run-over power equal more than 500 motors with power 58 KW. 42% of families in hamdan had been owned in agricultural well, while 58% of hamdan population (not own) could be used of agricultural wells.

EVALUATION AND MANAGEMENT OF WITHDRAWAL GROUND WATER FOR AGRICULTURE IN NIHM DIRECTORATE-YEMEN

The aim of this research was to evaluate and manage ground water withdrawal for agriculture in Nihm directorate, by studying random sample to measure and read the requirements data of agricultural Nihm wells. Annual ground water withdrawals for agricultural irrigation were compared with both of annual renewable ground water and actual crops water requirement in Nihm. Actual crops water requirements and irrigation scheduling, and quantity of water to be applied using surface and drip irrigation systems were done depending on each data of; Nihm climate, crop coefficients and soil type by using a computer program (FAO). The results showed – as sample:- that the annual volume of groundwater recharge was 21.813 MCM per year, while annual withdrawals volume of groundwater from all agricultural wells was found more than59 MCM per year for irrigating only 3118 ha. Thereby annual withdrawals of ground water was 270% the renewable groundwater, so annual decreasing rate of ground water level was found 0.3 m/year. In about 47% of Nihm wells the in-betweens distance among them were below 500m, Where, the distance average among wells in all directions was 560m. The total quantity of groundwater withdrawals for agricultural irrigation increase by 45% (26.4MCM) comparing by actual irrigation requirements calculated for cultivated crops in Nihm (about 32.57MCM) under surface irrigation system (60%efficiency). In addition, results shows that each one hectare receive 18922m3/year of withdrawal groundwater, as about 200% average actual irrigation required to irrigate one hectare by surface irrigation system or 250% average actual irrigation required to irrigate one hectare by modern irrigation systems. If drip irrigation system was applied with efficiency of 90% in substance to surface irrigation system to irrigate qat and grape, and also, if sprinkler irrigation system was applied in substance to surface irrigation to irrigate wheat, so the actual irrigation water required and withdrawal form groundwater will decreases from 32.57MCM/year to 22.887MCM/year, this resulting in saving 36.118MCM/year (62% of the annual groundwater withdrawal).

Light integral as an indicator of water use in commercial greenhouse nurseries

Irrigation strategies in pot plants of Kalanchoë blossfeldiana were studied in two commercial greenhouse nurseries by continuous weighing of plants on a high-precision balance. The objectives were to study actual irrigation strategies implemented by growers and to evaluate the method of continuous weighing as a potential tool for future irrigation management. Mean values of temperature, relative humidity, light, and weight were recorded every five minutes using data loggers. The change in weight over time was estimated and related to the calculated total canopy surface area of the studied plants. The rate of weight change was then statistically tested in relation to the recorded external factors. The factor with the strongest effect on total water-consumption rate over time was the light integral. As expected, water consumption was also affected by temperature and humidity, as well as the time of day. Although the growers indicated clear irrigation strategies, the study showed that these were not implemented in a true sense or correlated to the information available in greenhouse climate computers. The study also indicated that a high-precision weighing balance might be an important tool for future control of plant growth and plant architecture through irrigation in the pot plant industry.

EFFECT OF PULSE DRIP IRRIGATION ON YIELD AND WATER USE EFFICIENCY OF POTATO CROP UNDER ORGANIC AGRICULTURE IN SANDY SOILS

Pulse drip irrigation is a recent concept where small frequent irrigation applications are applied to saturate the soil and meet the plant water requirements. The field experiment was carried out during two summer growing seasons 2006 and 2007, it executed in Abo-Ghaleb farm, Cairo- Alex. Rood, 60 Km away from Cairo and the soil was sandy.Seed tubers were planted on 2 th of February and harvested on 28 th of May in two seasons,and the well water was used as irrigation source having EC 1.9 ds/m, the soil sample were taken up to 45 cm depth. Diameter of the lateral line was 16 mm (OD)with discharge of 2.1 l/h. The distance between emitters was 30 cm and between laterals was 70 cm. The present investigation aimed to study the effect of pulse drip irrigation under organic agriculture for saving water and increasing yield of The following parameters were studied to evaluate the performance of pulse drip irrigation :( 1) Soil moisture distribution, (2) Application efficiency AE, (3) Yield of potato YP, (4) Water use efficiency of potato WUE potato. The results indicated that wetted soil volume (more than or equal 100% of field capacity) in root zoneWSV≥100% FC, application efficiency, yield and water use efficiency of potatowere increased by increasing number of irrigation pulses where: (1) WSV≥100% FC in root zone increased from 9617 cm3 under continuous drip irrigation to maximum value where it become 14272 cm3 after applying pulse technique on 4pulses at 100 % from actual irrigation requirements under surface drip irrigation, recording an increase of 48%. (2)Maximum values of AE were 93.5%, 97% and 99.2% under 100 %, 75 % and 50% from IRa respectively with 4 pulses under surface drip irrigation. (3)YP increased from 4.70 (ton/fed.) under CDI to maximum value, where it become 6.57 (ton/fed.) after applying pulse technique with 4 pulses at 100 % from IRa under subsurface drip irrigation, recording an increase 40%.(4)Avoid using pulse technique at 50% fromirrigation requirementsbecause,small amount of irrigation water with more pulses with increasing in time-off will concentrate the salts around the plant especially under surface drip irrigation hence high decreasing in the yield of potato.(5)WUE potato increased from 1.59 (kg/m3) under CDI to maximum value, where it become 2.62 (kg/m3) after applying pulse technique with 4 pulses at 75 % from IRa under SSDI, recording an increase 65%, this mean that we can save 25% of actual irrigation requirements per season which equal 679 m3 from irrigation water.

Comparing theoretical irrigation requirement and actual irrigation for citrus in Florida

Florida ranks first in citrus production, with nearly 68% of all U.S. citrus growing in the season 2005–2006. Most of the citrus groves are located from central to south Florida, and agricultural irrigation permitting is regulated by three of Florida's five water management districts. Most of the permitting for citrus production in Highlands, Polk and Hillsborough counties is conducted by the Southwest Florida Water Management District (SWFWMD), and quantities are based on the District's AGMOD computer program. In 2003, the SWFWMD implemented new permit criteria so that permitted amounts were more representative of actual water use. This paper compares grower reported citrus irrigation water use in Highlands, Polk and Hillsborough counties from 1994 through 2005 with permitted and theoretical irrigation requirements calculated by a daily water balance. Two different sets of crop coefficients ( K c's) developed for citrus in Florida were compared in the daily soil water balance calculation of theoretical irrigation requirements. The percentage of irrigated area considered in this study ranged from 40 to 60% to simulate a range of grower practices. Meteorological data from two weather stations and additional rainfall information from 50 locations within the three counties was used in the water balance. Missing and error values in the meteorological historical record data were filled with weather generators. The multiannual average water consumption (including cold protection water use) from growers ranged from 243 (Hillsborough) to 406 mm (Highlands) and the multiannual average permitted irrigation requirement (without cold protection) ranged from 295 to 557 mm. The simulated gross irrigation requirements under different scenarios of location- K c-wetted area were variable but mostly lower than the limits established by the district, except for some scenarios in Polk County, whose maximum simulated irrigation value reached 578 mm year −1. In general, permitted limits recommended by the SWFWMD seem to be reasonable for the actual water use by growers in these counties.

Effects of global irrigation on the near-surface climate

Irrigation delivers about 2,600 km3 of water to the land surface each year, or about 2% of annual precipitation over land. We investigated how this redistribution of water affects the global climate, focusing on its effects on near-surface temperatures. Using the Community Atmosphere Model (CAM) coupled to the Community Land Model (CLM), we compared global simulations with and without irrigation. To approximate actual irrigation amounts and locations as closely as possible, we used national-level census data of agricultural water withdrawals, disaggregated with maps of croplands, areas equipped for irrigation, and climatic water deficits. We further investigated the sensitivity of our results to the timing and spatial extent of irrigation. We found that irrigation alters climate significantly in some regions, but has a negligible effect on global-average near-surface temperatures. Irrigation cooled the northern mid-latitudes; the central and southeast United States, portions of southeast China and portions of southern and southeast Asia cooled by ~0.5 K averaged over the year. Much of northern Canada, on the other hand, warmed by ~1 K. The cooling effect of irrigation seemed to be dominated by indirect effects like an increase in cloud cover, rather than by direct evaporative cooling. The regional effects of irrigation were as large as those seen in previous studies of land cover change, showing that changes in land management can be as important as changes in land cover in terms of their climatic effects. Our results were sensitive to the area of irrigation, but were insensitive to the details of irrigation timing and delivery.

In-season time series analysis of Resourcesat-1 AWiFS data for estimating irrigation water requirement

AWiFS sensor on board IRS-P6 (Resourcesat-1), with its unique features—wide swath and 5-day revisit capability provides excellent opportunities to carry out in-season analysis of irrigated agriculture. The study carried out in Hirakud command area, Orissa State indicated that the progression of rice crop acreage could be mapped through analysis of time series AWiFS data set. The spectral emergence pattern of rice crop was found useful to identify the period of rice transplantation and its variability across the command area. This information, integrated with agro-meteorological data, was used to quantify 10-daily canal-wise irrigation water requirement. A comparison with field measured actual irrigation supplies indicated an overall supply adequacy of 88% and showed wide variability at lateral canal level ranging between 18% and 109%. The supply pattern also did not correspond with the chronological variations associated with crop water requirement, supplies were 15% excess during initial part of season (December and January) and were 20.1% deficit during later part of season (February to April). Rescheduling the excess supplies of the initial period could have reduced the deficit to 15% during peak season. The study has demonstrated the usefulness of AWiFS data to generate the irrigation water requirement by mid-season, subsequent to which 38% supplies were yet to be allocated. This would support the irrigation managers to reschedule the irrigation water supplies to achieve better synchronization between requirement and supply leading to improved water use efficiency.

Prioritisation of parameters influencing residential water use and wastewater flow

ABSTRACT H. E. Jacobs (corresponding author)Department of Civil Engineering,University of Stellenbosch,Private Bag X1, Matieland 7602,South AfricaE-mail: hejacobs@sun.ac.zaJ. HaarhoffDepartment of Civil Engineering Science,University of Johannesburg,P.O. Box 524, Aucklandpark 2006,South AfricaTel.: +27 11 559 2148,Fax: +27 11 559 2395 A residential end use model (REUM) which accounts for indoor water demand, outdoor waterdemand, hot water demand, wastewater flow and the mass of total dissolved substances (TDS) inthe wastewater, was earlier described by the authors. The integral relationship between waterquality and quantity in the model allows for holistic modelling of different water demandmanagement measures’ effects. The model covers 16 independent micro-components of wateruse and requires numerous model parameters. This paper has the objective to prioritise the 79parameters which remain after stripping all possible redundancy from the model in terms of theirrelative impact. Two ranking criteria are used: the elasticity and the sensitivity of each parameter.The results, benchmarked to a typical South African suburban residence, show that householdsize is the most notable parameter for modelling the indoor water demand, hot water demandand wastewater flow volume. Pan evaporation and a factor describing actual lawn irrigation inrelation to theory are most notable for modelling the outdoor demand. Wastewater TDSconcentration is dominated by what is added at the toilet rather than pharmaceuticals andpersonal care products (PPCPs) added at other entry points to the wastewater system. Themethodology developed and results obtained underpin the view that effective water demandmanagement policies can only be rationally formulated with the assistance of a comprehensivewater and wastewater model based on micro-components of water use.

A distributed agro-hydrological model for irrigation water demand assessment

The actual irrigation water demand in a district in Sicily (Italy) was assessed by the spatially distributed agro-hydrological model SIMODIS (SImulation and Management of On-Demand Irrigation Systems). For each element with homogeneous crop and soil conditions, in which the considered area can be divided, the model numerically solves the one-dimensional water flow equation with vegetation parameters derived from Earth Observation data. In SIMODIS, the irrigation scheduling is set by means of two parameters: the threshold value of soil water pressure head in the root zone, h m, and the fraction of soil water deficit to be re-filled, Δ. This study investigated the possibility of identifying a couple of irrigation parameters ( h m, Δ) which allowed to reproduce the actual irrigation water demand, given that the study area was adequately characterized with regard to the spatial distribution of the soil hydraulic properties and the vegetation conditions throughout the irrigation season. The spatial distribution of the soil and vegetation properties of the study area, covering an irrigation district of approximately 800 ha, was accurately characterized during the summer of 2002. The soil hydraulic properties were identified by an intensive undisturbed soil sampling, while the vegetation cover was characterized in terms of leaf area index, surface albedo and fractional soil cover by analysing multispectral LandSat TM imageries. Irrigation volumes were monitored at parcel scale. A reference scenario with h m = −700 cm and Δ = 50% (corresponding to a mean actual to potential transpiration ratio of 0.95) allowed to reproduce the spatial and temporal distribution of the actual irrigation demand at the district scale. The spatial variability of the crop conditions in the considered area had much more influence to assess the irrigation water demand than the soil hydraulic spatial variability. The proposed approach showed that, under the agro-climatic conditions typical for the Mediterranean region, SIMODIS may be a valuable tool in managing irrigation to increase water productivity.

A Fuzzy-GAs Model for Determining Varied Irrigation Efficiency

Irrigation efficiency is necessary information in water resource management. We proposed fuzzy sets approach for estimating varied irrigation efficiency. Genetic algorithms technique was applied to calibrate membership function of fuzzy model. The fuzzy sets technique considered the uncertainty of the available water resource and required area as the input variables. The approach model was applied to determine the fluctuated irrigation efficiency of the Nong Wei Irrigation Project (in the Northeast region of Thailand). Results found that the fuzzy-GAs model can be used to obtain the irrigation efficiencies, given the total available water resources and requested irrigation-area. The GAs calibration provided the optimal condition of the proposed model. Moreover, the proposed approach can be given the irrigation efficiencies which are close to the actual irrigation efficiency. Further, the results indicate that the varied irrigation efficiency is more precise than the constant irrigation efficiency.

Financial viability and profitability of irrigation in Crimea, Ukraine

Following the collapse of the Soviet Union in 1991, the financial sustainability of irrigated agriculture in Crimea (Ukraine) has been endangered due to transitional problems. The undefined state of ownership, absence of secure agricultural markets and lack of farmers' funds for operations and maintenance resulted in irrigation equipment breaking down. Consequently, irrigation water demand has fallen dramatically. This paper looks at whether irrigated agriculture is financially viable and profitable in a market economy. By comparing the price paid for water delivery services with the actual irrigation water expenditure, it becomes clear that there is currently only partial cost recovery. By comparing returns to irrigation water with the potential costs of water delivery, it is clear that irrigation could be profitable in the future even in the most distant areas. It is interesting to note that on-farm costs account for a substantial share of the total potential irrigation costs and the challenge is therefore to reduce and fund on-farm costs.