Irrigation Zone Research Articles

Fuzzy control system for variable rate irrigation using remote sensing

Variable rate irrigation (VRI) is the capacity to spatially vary the depth of water application in a field to handle different types of soils, crops, and other conditions. Precise management zones must be developed to efficiently apply variable rate technologies. However, there is no universal method to determine management zones. Using speed control maps for the central pivot is one option. Thus, this study aims to develop an intelligent fuzzy inference system based on precision irrigation knowledge, i.e., a system that can create prescriptive maps to control the rotation speed of the central pivot. Satellite images are used in this study because remote sensing offers quick measurements and easy access to information on crops for large irrigation areas. Based on the VRI-prescribed map created using the intelligent decision-making system, the pivot can increase or decrease its speed, reaching the desired depth of application in a certain irrigation zone. Therefore, considering the spatial variability in the crop has made the strategy of speed control more realistic than traditional methods for crop management. The intelligent irrigation system pointed out areas with lower leaf development, indicating that the pivot must reduce its speed, thus increasing the water layer applied to that area. The existence of well-divided zones could be observed; each zone provides a specific value for the speed that the pivot must develop for decreasing or increasing the application of the water layer to the crop area. Three quarters of the total crop area had spatial variations during water application. The set point built by the developed system pointed out zones with a decreased speed in the order of 50%. From the viewpoint of a traditional control, the relay from pivot percent timer should have been adjusted from 70% to 35% whenever the central pivot passed over that specific area. The proposed system obtained values of 37% and 47% to adjust the pivot percent timer. Therefore, it is possible to affirm that traditional control models used for central-pivot irrigators do not support the necessary precision to meet the demands of speed control determined by the developed VRI systems. Results indicate that data from the edaphoclimatic variables when well-fitted to the fuzzy logic can solve uncertainties and non-linearities of an irrigation system and establish a control model for high-precision irrigation.

Досвід захисту сільських населених пунктів від підтоплення у зоні зрошення

Досвід захисту сільських населених пунктів від підтоплення у зоні зрошення

Evaluating On-demand Irrigation Systems for Container-grown Woody Plants Grown in Biochar-amended Pine Bark

Controlling irrigation using timers or manually operated systems is the most common irrigation scheduling method in outdoor container production systems. Improving irrigation efficiency can be achieved by scheduling irrigation based on plant water needs and the appropriate use of sensors rather than relying on periodically adjusting irrigation volume based on perceived water needs. Substrate amendments such as biochar, a carbon (C)-rich by-product of pyrolysis or gasification, can increase the amount of available water and improve irrigation efficiency and plant growth. Previous work examined two on-demand irrigation schedules in controlled indoor (greenhouse) environments. The goal of this study was to evaluate the impact of these on-demand irrigation schedules and hardwood biochar on water use and biomass gain of container-grown Hydrangea paniculata ‘Silver Dollar’ in a typical outdoor nursery production environment. Eighteen independently controlled irrigation zones were designed to test three irrigation schedules on ‘Silver Dollar’ hydrangea grown in pine bark amended with 0% or 25% hardwood biochar. The three irrigation schedules were conventional irrigation and two on-demand schedules, which were based on substrate physical properties or plant physiology. Conventional irrigation delivered 1.8 cm water in one event each day. The scheduling of substrate-based irrigation was based on the soilless substrate moisture characteristic curve, applying water whenever the substrate water content corresponding to a substrate water potential of –10 kPa was reached. The plant-based irrigation schedule was based on a specific substrate moisture content derived from a previously defined relationship between substrate moisture content and photosynthetic rate, maintaining the volumetric water content (VWC) to support photosynthesis at 90% of the maximum predicted photosynthetic rate. Total water use for the substrate-based irrigation was the same as for the conventional system; the plant-based system used significantly less water. However, plant dry weight was 22% and 15% greater, water use efficiency (WUE) was 40% and 40% greater, and total leachate volume was 25% and 30% less for the substrate-based and plant-based irrigation scheduling systems, respectively, than for conventional irrigation. The 25% biochar amendment rate reduced leachate volume per irrigation event, and leaching fraction, but did not affect total water use or plant dry weight. This research demonstrated that on-demand irrigation scheduling that is plant based or substrate based could be an effective approach to increase WUE for container-grown nursery crops without affecting plant growth negatively.

Production of Thuja (T. standishii x T. plicata) Using an Automated Micro-Irrigation System and Routine Leaching Fraction Testing in a Container Nursery1

Abstract A web-based, container irrigation scheduling program (CIRRIG) based on routine Leaching Fraction (LF=drainage/applied) testing and real-time weather monitoring was evaluated for its effect on plant growth and water use of Thuja (T. standishii x T. plicata) ‘Green Giant' in #15 [43 cm (17 inch)] containers in a commercial nursery in Florida. Independently-controlled irrigation zones each containing 830 plants were irrigated automatically with CIRRIG or with the nursery's traditional irrigation practice of a fixed daily rate. After 6 months, CIRRIG reduced the total volume of water applied by 51% [490 vs. 990 L/plant (129 vs. 262 gal/plant) but reduced growth in plant height and width by 15% and 10%, respectively. Routine LF testing indicated that the target LF of 25% was likely too low for the coarse pine bark substrate and spray-stake irrigation system. In light of stricter consumptive use permitting of water by governmental agencies, technologies such as CIRRIG may allow nurseries to produce more plants with less water. Index words: CIRRIG, evapotranspiration, growth, landscape plant, programmable logic controller, water use Species used in this study: Thuja Green Giant [Thuja (T. standishii x T. plicata) ‘Green Giant']

Spatial distribution of heavy metals in crops in a wastewater irrigated zone and health risk assessment

Industrialization and urbanization have produced a large amount of wastewater. Part of the municipal wastewater has been used as an irrigation source in urban/suburban areas. Its utilization, although economically beneficial, can significantly deteriorate the integrity of the ecological systems (e.g., in terms of quality of soil and resulting food products). The objectives of this study are to investigate the spatial distribution and bio-accumulation of heavy metals (e.g., Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) in food crops (and topsoil) and associated health risks of their consumption in the area of Mangla Dam, Pakistan. To this end, studies were conducted to assess the risk factors such as the bioconcentration factor (BCF), health risk index (HRI), and daily intake of heavy metals (DIM). Accordingly, there was more contamination in Mangla Dam water irrigated zone (DWI) than in the groundwater irrigated zone (GWI). Co exhibited the maximum BCF of 7.45 for Eruca sativa and 6.61 for Brassica campestris in the GWI zone. Likewise, enhanced risk to human health was seen from of Cd, Cr, and Pb in Triticum aestivum and Eruca sativa grown in the DWI zone. It is recommended that the quality profile of wastewater discharge into freshwater ecosystems should be continuously monitored and regulated.

Stability Analysis of Flood Bunds: A Study on Geotechnical Health Evaluation of Embankments

Flood constitutes one of the world’s most serious environmental hazards. Flood bunds are the earthen hydraulic structures which are constructed along the River to control the Flood water to avoid damages to the infrastructures, crops, livestock and loss of human lives. Pakistan which lies in the Indus Basin has been facing severe threats and losses from the floods since histories. About 6807km length of flood embankment has been constructed to safeguard against the floods in the country. Punjab has been worst hit province by heavy floods and rains causing heavy loss. Geotechnical Evaluation is vital for proper functioning of such structures. In this study four flood bunds susceptible to potential embankment breaching during flood have been selected along river Chenab in district Muzaffar Garh Irrigation zone. Suite of analysis using GeoStudio software (SLOPE/W and SEEP/W for stability and seepage analysis respectively) has been performed by considering four different critical scenarios, (1) steady state at highest flood level (2) rapid drawdown from highest flood level (3) steady state at extreme condition with 3 feet free board (4) rapid drawdown from extreme condition with 3 feet free board. The safety of the flood bunds is evaluated in terms of River Embankment Breaching Vulnerability Index (REBVI), safe exit gradient and factor of safety against slope failure. Based on these calculated factors from the numerical analysis it is found that embankment at RD:25,29 are marginally safe, whereas at RD: 147, 157 are susceptible to pipping failure. Therefore, it is recommended to make embankment impervious using cohesive material and to install cut-off walls or berms to lengthen the seepage path.

Selecting rootstocks to improve vine performance and vineyard sustainability in deficit irrigated Monastrell grapevines under semiarid conditions

Regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) were compared for five years, in field-grown mature Monastrell grapevines grafted on five different rootstocks (140Ru, 1103 P, 41B, 110R, and 161-49C), in the semiarid winegrowing region of D.O. Bullas, South Eastern Spain. Vines grafted on invigorating rootstocks (140Ru or 1103 P) showed the highest vigor, water productivity, and productive water use efficiency (WUEyield), but at the expense of berry quality (lower berry quality indices, QI), compared to those on rootstocks of medium-low vigor (41B, 110R, and 161-49C). Vines grafted on 41B showed a moderate vigor-yield-efficiency-quality response, and this did not improve substantially the final berry quality. The least vigorous rootstocks (161-49C and 110R) gave lower yield, WUEyield, and productivity ratios, but a significant improvement in long-term final berry quality. The PRI increased the yield and/or berry quality attributes, especially in low vigor rootstocks (161-49C, 110R) and high vigor rootstocks (140Ru, 1103 P), but not in the medium vigor rootstock 41B. In addition, PRI produced a beneficial increase in the nutraceutical potential for practically all rootstocks. The PRI vines grafted on 161-49C gave the lowest yield and WUEyield, but the highest QI scores and the highest nutraceutical value, while PRI vines grafted on 110R had enhanced long-term yield, WUEyield, and amino acid and resveratrol contents, with similar berry quality (QI) indices, compared to RDI vines. Both 161-49C and 110R seem good options to achieve a compromise between long-term yield-quality-efficiency and returns for the grower. The application of low water volumes (85-90 mm year−1) with well-designed DI strategies was enough to maintain the vines in an optimum physiological state, obtaining moderate yields (7,400–9,900 kg ha−1, for 161-49C and 110R) with high berry quality and nutraceutical potential for premium red wine production. Such an approach can serve as an adaptation measure in the face of climate change, to improve vine performance and enhance Monastrell vineyard sustainability under semiarid and water limiting conditions.

Irrigation with sediment-laden river water affects the soil texture and composition of organic matter fractions in arid and semi-arid areas of Northwest China

Soil organic carbon (SOC) is the largest reservoir of organic carbon in the terrestrial ecosystem, and is an effective mean of enhancing crop production in the irrigated area of the arid and semi-arid regions. Understanding long-term changes in composition of SOM under irrigation from sediment-laden Yellow River water is essential to manage sustainability issues in the agro-ecosystem. A total of 45 soils, including 39 of irrigated fields differing in irrigation history and 6 of non-cultivated and non-irrigated natural fields as the control, were sampled at 0–20 cm depth. The soil was analyzed for total SOC content, partitioning of light (LFOM) and heavy (HFOM) fraction organic matter based on NaI solution density of 1.7 g m3 and for particle size distribution. Compared to the non-irrigated and non-cultivated control soil, the LFOM and HFOM in irrigated soils increased with the duration of irrigation though SOM existed dominantly as the heavy fraction. The soils irrigated for <50 years have overall lesser LFOM and HFOM and more sand compared to those with >50 years irrigation. Further, a positive relationship existed between the fine particle and the SOM or its fractions (negative relation with coarse particle) suggesting either SOM accumulated as fine particles or the fine mineral particles better preserved SOM. In addition, field soil moisture at the time of sampling during October 2009 correlated with HFOM (p < 0.001) and LFOM (p < 0.01). The study suggested that the long-term irrigation with water diverted from Yellow River increased fine particle, SOC and the light and heavy fraction in the Ningxia Irrigation Zone.

Effects of Irrigating with Saline Water on Soil Salinization (Eastern Tunisia)

This study was conducted in the irrigation zone of ‘Zelba’, located in the Region of Mahdia (Eastern Tunisia). The main objective of the study is to investigate the effect of irrigating with saline water on soil properties. Soil sampling was carried out to a depth of 150 cm, with samples being collected from 20 plots. Two soil profiles were drilled in each plot. The first profile was taken from an irrigated area, where water salinity is around 7 mS/cm. The second profile was taken from a non-irrigated area. Salinity maps were developed using a kriging method. Soil characterization revealed that the soil is of a deep isohumic type with silty to silty-clay texture. The analysis results showed the presence of a high sodicity level. In fact, soil adsorption ratio and exchangeable sodium percentage exceeded the acceptable thresholds, being 10 and 15%, respectively. Salinity mapping of five soil layers showed little change of soil salinity for all the examined 20 plots. Nevertheless, the highest salinity levels occurred in the deepest layers of the southwestern part of the studied irrigation zone. For instance, the electric conductivity was shown to vary between 1.5 and 1.7 mS/cm, in the irrigated profile, while it varied between 1.5 and 2.6 mS/cm, in the non-irrigated profile. The low salinity observed in the north of the study area could be explained by the fact that this part is closer to the water well. Moreover, compared to irrigated zones, the non-irrigated areas are characterized by a higher level of salinity. Irrigation lowered the salinity of the irrigated area through salts leaching. Monitoring of soil salinity and sodicity over time proved an enrichment of soil by salts and exchangeable Na $$^{+}$$ content. This trend is attributed to the application of saline irrigation water.

ON THE IRRIGATION REGIME OF AGRICULTURAL CROPS

The article presents a comparative analysis of the results of long-term fundamental and applied researches to establish the total water consumption and irrigation regime of cotton crops in the irrigated zone of Zakavkazye (Azerbaijan) and Central Asian countries. It is marked their adequacy in determining the water demand of plants and suggested the necessity of transition to methods widely used in the world.

Effects of straw application on nitrate leaching in fields in the Yellow River irrigation zone of Ningxia, China

A five-year field experiment was conducted to investigate the effects of straw application on nitrate leaching loss. Treatments included soil that was not treated (control), soil treated with straw at a low rate (4,500 kg ha−2, T1) and soil treated with straw at a high rate (9,000 kg ha−2, T2). Nitrate-nitrogen leaching in the 10, 20, 30, 60, and 90 cm soil layers was measured using the resin-core method. The results indicated that straw application could reduce soil nitrate leaching losses in the 0–30 cm layer. In this layer, the nitrate leaching values for T1 (13.76 kg ha−2) and T2 (13.74 kg ha−2) were both significantly lower than those of the control (15.76 kg ha−2) (P < 0.05); the soil nitrate leaching losses decreased by 12.71% and 12.84% for those two treatments, respectively. However, no significant differences in losses were observed (P > 0.05) between T1 and T2. The effects of straw application were apparent only in the ploughing layer (30 cm-depth soil layer). In the deeper layers (60 and 90 cm), no significant differences were observed between the treatments and the control, and the same results were observed in the topsoil layers (10 and 20 cm).

Soil Water Dynamics of Shallow Water Table Soils Cultivated With Potato Crop

Core Ideas Estimation of water table level supplies upward water flux for daily ETc needs. Episodic master recession method informs water table control during rain events. Water table recession varies by soil and irrigation, with fastest rates under subirrigation. Irrigation depth may be reduced in sprinkler areas with water table management. Agricultural areas with shallow water tables usually rely on upward soil water flux to supply crop evapotranspiration (ETc). The study objective was to determine optimum water table levels for coarse‐textured soils cultivated with potato (Solanum tuberosum L.) by estimating the upward soil water flux under different irrigation methods. Potato was grown under seepage, subirrigation with tile drainage, subsurface drip irrigation (SDI), and sprinkler irrigation. Irrigation zones were classified as sandy soil with low soil organic matter (SOM) and high bulk density (Bd), or loamy sand soil with high SOM and low Bd. Upward soil water flux supplied enough water to the root zone to meet ETc when the water table was at the 69‐cm depth for loamy sand soils under seepage, and 42 and 45 cm for sandy soils under subirrigation and SDI, respectively. The sprinkler‐irrigated area had no control over the water table, whereby the cumulative contribution of upward water flux still averaged 6.3 cm, suggesting that irrigation rates could be reduced if the water table is controlled and upward flux accounted for in the crop water balance. Rainfall introduces flooding risks and crop losses, but these risks are minimized with management. The water table elevation/precipitation ratio was 34.4 and 25.6 cm cm−1 of rain for loamy sand and sandy soils. After precipitation, the water table returned to the original levels twice as fast under subirrigation than with other methods given improved drainage capacity. Soil characteristics, irrigation method, upward water flux, and proper water table management are important factors for maintaining ideal soil moisture conditions in the crop root zone, minimizing flooding risk.

Effects of extremely-late sowing on the grain yield, nitrogen uptake and utilization, and grain protein content in winter wheat

In order to explore the cultivation techniques for high yield, quality and nitrogen use efficiency of wheat and guide the production practice of late sowing, a two-year experiment of different sowing times and plant densities in fixed plots was conducted from October 2012 to June 2014. Weak-spring cultivar of Yanzhan4110 (YZ4110) and semi-winter cultivar of Aikang58 (AK58) were sowed with two cropping patterns: Normal sowing (sowing in the middle of October, 2.4×106 plants·hm-2) and extremely-late sowing (sowing in the middle of November, 6.0×106 plants·hm-2). The nitrate-N content in 0-40 cm soil, the nitrogen (N) uptake and utilization, grain yield, grain protein content and N uptake efficiency in winter wheat were investigated. Compared with normal sowing, extremely-late sowing significantly increased the nitrate-N content in 0-40 cm soil at jointing and anthesis stages, which in turn promoted the N uptake and accumulation of plants after jointing stage and increased the N distribution ratio of spikes at maturity. As a result, the grains with extremely-late sowing had higher protein contentin both YZ4110 and AK58, and higher protein yield and N uptake efficiency in YZ4110 than that with normal sowing. However, the effects of extremely-late sowing on grain yield were different in the two cultivars. Compared with normal sowing, extremely-late sowing clearly raised the grain yield of YZ4110, but significantly decreased that of AK58. These results indicated that extremely-late sowing is an alternative cropping technique to increase grain yield and protein content for winter wheat in irrigation zones through maintaining the soil N supply after jointing stage and increasing N uptake efficiency.

Status quo and present challenges of the sustainable use and management of water and land resources in Central Asian irrigation zones - The example of the Navoi region (Uzbekistan)

Soil salinization is a major problem in many arid and agriculturally used regions and Central Asia is a prime example for this. Intensive irrigation, saline water resources, shallow groundwater tables and high evapotranspiration rates lead to the enrichment of salts in the top soils and a reduced soil productivity in the Central Asian lowlands. This is aggravated by a strong socioeconomic growth which results in an increase in the water consumption and the intensification of the farming practices (e.g. fertilizer application). This article analyses these problems for the Navoi province in Uzbekistan, a region located in the lower reaches of the Zarafshan River in the Kyzyl Kum desert. Between 2000 and 2015 detailed data on the groundwater table, groundwater salinity and the soil salinity were collected, complemented by meteorological data, soil characteristics, water use, and fertilizer statistics. Based on these datasets the ameliorate soil conditions in the Navoi irrigation zone and their temporal dynamic were assessed.The results show that both the groundwater and soil salinity have improved slightly during the last 15 years. Especially the percentages of samples with a high salinity have been reduced significantly. In 2015 only 0.7% of the irrigated soils have been categorized as highly saline while 71.3% were only slightly saline and 18.3% non-saline, while those values for the year 2000 were 6.1%, 51.5%, and 13.2%. The ameliorate soil conditions, on the other hand, have not improved accordingly, but showed a slight deterioration, even if they are overall satisfactory in 79.6% of the area. The percentage of irrigated soils with an unsatisfactory condition has increased from 3 to 13.9% between 2000 and 2014. This development is not related to any climatological, soil or groundwater parameters, so that the impacts of an increased water usage for urban and industrial purposes (and the related effects on the water quality), as well as the increased fertilizer application, seem to be a possible explanation for the observed trend.The results show the impact of the low efficiency of the irrigation and drainage system, which is outdated, not well maintained and thus often failing, on the groundwater level and the soil salinization, but also how the attempts to update the system during the recent years has led to a slight improvement of the soil and groundwater salinity.

Evaluation and Aggregation Properties of Thermal Infra-Red-Based Evapotranspiration Algorithms from 100 m to the km Scale over a Semi-Arid Irrigated Agricultural Area

Evapotranspiration (ET) estimates are particularly needed for monitoring the available water of arid lands. Remote sensing data offer the ideal spatial and temporal coverage needed by irrigation water management institutions to deal with increasing pressure on available water. Low spatial resolution (LR) products present strong advantages. They cover larger zones and are acquired more frequently than high spatial resolution (HR) products. Current sensors such as Moderate-Resolution Imaging Spectroradiometer (MODIS) offer a long record history. However, validation of ET products at LR remains a difficult task. In this context, the objective of this study is to evaluate scaling properties of ET fluxes obtained at high and low resolution by two commonly used Energy Balance models, the Surface Energy Balance System (SEBS) and the Two-Source Energy Balance model (TSEB). Both are forced by local meteorological observations and remote sensing data in Visible, Near Infra-Red and Thermal Infra-Red spectral domains. Remotely sensed data stem from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and MODIS sensors, respectively, resampled at 100 m and 1000 m resolutions. The study zone is a square area of 4 by 4 km2 located in a semi-arid irrigated agricultural zone in the northwest of Mexico. Wheat is the dominant crop, followed by maize and vegetables. The HR ASTER dataset includes seven dates between the 30 December 2007 and 13 May 2008 and the LR MODIS products were retrieved for the same overpasses. ET retrievals from HR ASTER products provided reference ET maps at LR once linearly aggregated at the km scale. The quality of this retrieval was assessed using eddy covariance data at seven locations within the 4 by 4 km2 square. To investigate the impact of input aggregation, we first compared to the reference dataset all fluxes obtained by running TSEB and SEBS models using ASTER reflectances and radiances previously aggregated at the km scale. Second, we compared to the same reference dataset all fluxes obtained with SEBS and TSEB models using MODIS data. LR fluxes obtained by both models driven by aggregated ASTER input data compared well with the reference simulations and illustrated the relatively good accuracy achieved using aggregated inputs (relative bias of about 3.5% for SEBS and decreased to less than 1% for TSEB). Results also showed that MODIS ET estimates compared well with the reference simulation (relative bias was down to about 2% for SEBS and 3% for TSEB). Discrepancies were mainly related to fraction cover mapping for TSEB and to surface roughness length mapping for SEBS. This was consistent with the sensitivity analysis of those parameters previously published. To improve accuracy from LR estimates obtained using the 1 km surface temperature product provided by MODIS, we tested three statistical and one deterministic aggregation rules for the most sensible input parameter, the surface roughness length. The harmonic and geometric averages appeared to be the most accurate.

Effect of Nitrate Leaching Caused by Swine Manure Application in Fields of the Yellow River Irrigation Zone of Ningxia, China

A five-year swine manure application trial and a study of nitrate leaching losses have been conducted. There were three treatments: traditional without manure (CK), traditional matched manure 4500 kg ha−2 (T1) and traditional matched manure 9000 kg ha−2 (T2). Nitrate nitrogen leaching losses at the 30-, 60-, and 90-cm soil layers were measured using the resin core method. The results indicate that the swine manure application did not noticeably increase soil nitrate leaching losses in the 30-cm layer. T1 (16.85 ± 0.40 kg ha−2) and T2 (17.01 °C0.46 kg ha−2) were not significantly different than CK (15.96 ± 0.41 kg ha−2) (P < 0.05), which was also the case at the 60-cm layer. However, there are significant differences between the treatments and CK at the 90-cm layer, although there were no significant differences between T1 and T2 in that layer. The application of manure can increase soil organic matter (SOM) and total nitrogen (TN). The SOM of T1 and T2 were increased to 0.95 g kg−1 and 1.41 g kg−1, respectively. The TN values of CK, T1 and T2 were 0.72, 0.78 and 0.88 g kg−1, respectively, in the 0 to 30 cm layer, and were improved by 7.72% and 22.04%.

Seasonal Hydrochemical Characterization and Groundwater Quality Delineation Based on Matter Element Extension Analysis in a Paper Wastewater Irrigation Area, Northwest China

The current study was carried out to delineate the seasonal hydrochemical characteristics and to quantify the suitability of groundwater for drinking and irrigation purposes in an alluvial plain adjacent to a paper wastewater irrigation zone, northwest China. Groundwater samples were collected from 14 groundwater monitoring wells in pre-monsoon, monsoon and post-monsoon seasons, respectively. Statistical analysis and Chadha diagram were used to delineate the groundwater hydrochemical characteristics. The matter element extension analysis (MEEA) model was proposed to quantify the overall groundwater quality. Irrigation water quality indicators were applied to assess the suitability of groundwater for irrigation purpose. The research results show that the hydrochemical facies for the majority of the groundwater samples is SO4·Cl–Na type with some minor hydrochemical facies of HCO3–Ca·Mg, HCO3–Na, and Cl·SO4–Ca·Mg types. The sequences of ions are Na+ > Ca2+ > Mg2+ > K+ for cations, and HCO3 − > Cl− > SO4 2− > CO3 2− for anions. The major ions and contaminants in the groundwater are controlled by multiple factors including hydrogeological conditions, rock weathering, water–rock interactions and human activities. The values of pH, TDS and TH show reduction in the monsoon season, indicating slight improvement of water quality during the monsoon season. Water quality assessment results based on MEEA show that the overall groundwater quality in the wastewater irrigation zone is generally fair to poor quality. Some groundwater samples are even classified as very poor quality, which is unsuitable for human consumption. They are also unsuitable for irrigation because of potential sodium hazard and salinity hazard. Groundwater from the Yellow River irrigation zone and the alluvial plain is generally suitable for domestic and irrigation uses. Some local water sampling locations may experience water quality improvement during the monsoon season, which, however, will generally not affect the final water quality classification for domestic and irrigation purposes. Interestingly, the study also finds that the variation trend of the correlation degree computed from MEEA can be useful in determining water quality improvement. This study may provide insights for people to make educated decisions in efficient groundwater quality protection and sustainable groundwater quality management.

Economic assessment of an integrated drainage management system for a regional irrigation-drainage network

AbstractThe disposal of the excessive volume of degraded water coming from agricultural drainage systems is a serious environmental and economic issue, since a significant load of agrochemicals and salts contaminates water bodies downstream. An integrated on-farm drainage management (IFDM) system is an effective method of treatment by successively irrigating zones with drainage water. Each zone is cultivated with crops that have increasing tolerance to salinity, so that the drainage water effluents are minimized to an extent that the final drainage water volume is collected into an evaporation pond. The methodology of the system is proposed herein for a regional irrigation-drainage network (E1 in Agoulinitsa irrigation district in western Greece) as a method of reducing the disposal of agrochemicals in the coastal environment. Based on the design principles of an IFDM system, both the surface area of every irrigation zone and the costs of installing and operating the system are assessed. A scenario regarding the volume of drainage water that must be treated is examined as a sensitivity analysis. The results show that almost 15% of the cultivated area must be bounded for non-productive uses, resulting in a significant economic impact on the net present value of the investment.

Spatiotemporal variation of groundwater quality in an arid area experiencing long-term paper wastewater irrigation, northwest China

Groundwater is crucial for multiple uses over the world, especially in arid and semiarid regions. However, human activities significantly decreased groundwater quality. In this study, the spatiotemporal variation of groundwater quality was evaluated in an arid area where long-term paper wastewater irrigation has been implemented. For this study, seven wells were regularly monitored for physicochemical parameters over a period of 1 year. Statistical and graphical approaches were applied to interpret the spatiotemporal variation of groundwater quality parameters in the wastewater irrigation zone. Correlation analysis was also carried out to reveal the sources of some major ions. The results indicate that the groundwater type in the study area is dominated by the Cl–Na, followed by the HCO3–Na, the HCO3–Ca·Mg, and the SO4·Cl–Ca·Mg types. Groundwater in the area is significantly contaminated locally with fluoride, nitrite and ammonia, and the chemical oxygen demand levels were increased in some groundwater monitoring wells. Most contaminants showed an increasing trend from the Yellow River water irrigation zone toward the wastewater irrigation zone. Rock weathering, mineral dissolution, and cation exchange are important processes controlling groundwater quality, but human activities, such as wastewater irrigation, play an undeniable role in affecting groundwater quality in this area. The results of this study contribute to the understanding of the formation and circulation of groundwater under human activities and provide a scientific basis for regional water quality evaluation, water quality improvement, and protection.

Modeling water needs and total irrigation depths of maize crop in the south west of France using high spatial and temporal resolution satellite imagery

Climate change is projected to increase water resources limitation and to impact significantly agricultural production. A big challenge for agriculture will be to reduce the amount of water used to fit the environmental constraints, while maintaining a level of production that ensure food security. In this context, we develop a methodology based on high spatial and temporal resolution remote sensing data combined with a semi-empirical crop model coupling the Simple Algorithm For Yield estimates (SAFY, Duchemin et al., 2008, 2015) with the new formulation (Battude et al., 2016) to a water balance model adapted from the FAO-56 method (Allen et al., 1998). A module was added to automatically simulate irrigation. The model was used to assess the dynamics of actual Evapotranspiration (ETca) and water supplies of maize crop over large areas and during contrasted climatic years in the south west of France. It was first calibrated and evaluated over an experimental field using four years of ETca measurements. The validation was done over 18 maize fields and larger irrigated zones (135ha to 450ha) using total irrigation depths. This work permitted to quantify the ability of different methods to estimate the storage capacity (soil map vs in situ data) and the basal crop coefficient Kcb (standard vs remotely sensed values) and their impact on total irrigation depths. Good estimations were obtained for ETca (R=0.88; RRMSE=20%). The model also reproduced correctly the total irrigation depth over the 18 maize fields (R=0.79; RRMSE=18.8%) and three larger irrigated zones (R=0.8; RRMSE=42%). The underestimation (Bias=−93mm) is due to several reasons such as errors in soil water storage capacity estimates, but also to an overestimation of water needs by water managers or a potential over-irrigation carried out by farmers. Finally, the work demonstrates the high potential of combining a simple agro-meteorological model using only few parameters with satellite imagery for a large-scale monitoring of total irrigation depth.