Sensitivity of Irrigation Water Requirement to Climate Change in Arid and Semi-Arid Regions towards Sustainable Management of Water Resources

This study aimed to assess the spatiotemporal sensitivity of the net irrigation water requirement (NIWR) to changes in climate, for sixteen crops widely cultivated in four irrigation projects located in arid and semi-arid regions of Iraq. Using LARS-WG and five GCMs, the minimum and maximum temperature and precipitation were projected for three periods from 2021–2080 with 20-year steps (P1, P2, and P3) under representative concentration pathways (RCPs) 2.6, 4.5, and 8.5. Weather data available for a reference period from 1990–2019 in four representatives’ meteorological stations were used. The climate variables and other required data were inserted into the CROPWAT 8 NIWR tool. Findings revealed that the increase in the NIWR for the considered crops due to climate change falls in the range 0.1–42.4%, 1.8–44.5%, 1.2–25.1%, and 0.7–14.7% for the North Jazeera Irrigation Project (NJIP), Kirkuk Irrigation Project (KRIP), Upper Khalis Irrigation Project (UKIP), and Dalmaj Irri-gation Project (DLIP), respectively. Barley is more susceptible to changes in climate, whereas maize, potato, soybean, and millet are found to withstand changes in climate better than others. The novel outcomes of this study support optimal spatiotemporal allocation of irrigation water requirement and the sustainable management of water resources in a changing climate in arid and semi-arid regions.

Estimating evapotranspiration and irrigation water requirement in phonology stages of grape (VitisVinifera) using agro-hydrological model and remote sensing techniques

This study aims to compare the remote sensing (RS) approach and an agro-hydrological model to estimate evapotranspiration (ET) and irrigation water requirement (IWR) in semi-arid region, and the effect of vineyards management and their ages on these parameters. In the study region, after vineyards were classified into three main scenarios based on three vineyards ages (12-15, 15-18 and 18-21 years) and two management approaches (proper and improper management), ET and IWR were determined in each scenario using the Soil-Water-Atmosphere–Plant (SWAP) Model and Surface Energy Balance Algorithm for Land (SEBAL) for the year of 2019-2020 with Landsat8 images. While the accumulated ET calculated with SEBAL was compared with a field water balance, the results showed that without calibration or parameter optimization, the accumulated ET estimated with SEBAL exceeded that computed with SWAP. According to the findings, the most and least RMSE was related to August (1.32) and June (1.26). Analyses of scenarios showed that at the first stage of phonology (bud-break to bloom), the S3 scenario has the most IWR for each pixel (900 m2) by 2.7 m3, and at the second stage (bloom to ripening) and the third stage (ripening), the S1 scenario by 229.5 m3 and 78 m3 has the highest IWR, respectively.

Climate Change Effect on Irrigation Water Requirement of Wheat and Maize in Northern Part of Bangladesh

Bangladesh is one of the most vulnerable countries for climate change in agricultural water management. A research had been done to assess climate change effects on irrigation water use of wheat and maize in the northern part of Bangladesh. The twenty nine years of data (1990-2018) were analyzed with Mann-Kendall test as well as Sen’s slope for climate change impact and the responsible weather parameters due to climate change were identified with correlation coefficients. The crop water requirement of wheat in Bogura and Rangpur was declining at the rate of 3.3mm and 2.3mm per decade respectively. Net irrigation water requirement of wheat at both Bogura and Rangpur was inclining at the rate of 1mm and 10mm per decade respectively because the effective rainfall of these regions was decreasing at 5mm and 11mm per decade respectively. The crop water requirement of maize for similar districts was increasing at the rate of 3.2mm and 2.5mm per decade respectively although net irrigation water requirement had statistically non-significance for climate change effect. The weather parameter, which was mainly responsible for climatic change in irrigation water requirement, was increasing temperature. Therefore, wheat cultivation might be coped with climate change in the northern part of Bangladesh rather than maize on the basis of irrigation and water management.

Analysis of irrigation system performance based on an integrated approach with Sentinel-2 satellite images

The improvement of performance of irrigation systems plays a fundamental role in increasing their efficiency in order to reach a sound use of irrigation water. The COPAM (Combined Optimization and Performance Analysis Model) has proven its usefulness in performance evaluation of on-demand irrigation systems; however, in many cases, input data, such as water volumes delivered by hydrants, is not readily available. To support a wider application of the COPAM, we tested the possibility of using irrigation volumes estimated by means of space-borne remote sensing. The Sentinel-2 (S2) constellation provides high spatial resolution images with a frequency between 2 and 5 days, which is compatible with COPAM input requirements. In the present work, an irrigation sector in the Capitanata irrigation network (Foggia Province, no. 6 of District 10) in Italy was chosen to assess its performance by using COPAM with volumes estimated from Sentinel-2 data. As an input of COPAM, the upstream discharge was determined after a proper transformation of the estimated irrigation water requirement volumes and the recorded volumes into flowrates. The estimation of the irrigation water requirement volumes was accomplished through the estimation of crop evapotranspiration, Etcrop, and effective precipitation, Pn, by combining crop parameters (leaf area index - LAI, fractional vegetation cover - fc, and Albedo) derived from S2 images and the meteorological data from the ERA5 single levels reanalysis dataset collected for the whole study period, from June 1st to September 30th, 2019. The study comprised a comparison of the estimated irrigation water volumes and the corresponding recorded volumes. The results showed a good agreement between the estimated and the registered volumes in a large time scale for 10 days and a one-month period, while a large difference was observed in a daily time scale. The performance analysis was carried out for the overall system and at hydrant level. The estimated discharge was lower than the registered discharge, indicating better performance. Last but not least, some recommendations were proposed for improving performance in critical zones.

Potentials and limitations of climate change adaptation with crop calendar optimization in rice-based multiple cropping systems

<p>Climate change poses increasing risks to global food security with more severe heat stress, water scarcity, and flooding. As one of the major adaptation measures, adjusting crop calendars could be a feasible and effective solution to avoid adverse effects on crop yield potentials in a changing climate by allowing crops to grow in more favorable weather conditions. Previous single-crop and single-objective studies on the optimization of crop planting dates lack comprehensive consideration of multi-crop rotation systems, especially rice-based cropping systems with short growing season intervals in Asian tropical monsoon regions. This study seeks to better understand potentials and limitations of adjusting crop calendars for climate change adaptation of double-rice and rice-wheat rotation systems, with a particular focus on the following questions: (1) Is it possible to avoid yield loss of rice and wheat through adjusting crop calendars in the study area? (2) How will fallow period between crop growing seasons change in the future? (3) What are relationships between crop yield improvement, irrigation water requirement, and heat stress mitigation in the study area?</p><p>To address these questions, we calibrated a spatial implementation of the Environmental Policy Integrated Climate (EPIC) agronomic model to estimate annual potential yields, irrigation water requirement, and heat stress days of irrigated double-rice and rice-wheat cropping systems in Bangladesh, India, and Myanmar (the BIM countries), and adjusted crop calendars (a) by single-objective optimization with maximum yield and (b) multi-objective optimization with least irrigation water requirement, minimum heat stress days, and highest potential yield under climate change.</p><p>Our results indicate that most yield loss in rice and wheat could be avoided through shifting planting dates while considering effects of elevated atmospheric CO<sub>2</sub> concentration on biomass assimilation and transpiration. The model indicates that fallow periods between kharif-rice harvest dates and rabi-rice planting dates in double-rice systems are likely to become longer due to shorter growing season duration meanwhile fallow periods between kharif-rice harvest dates and rabi-wheat planting dates in rice-wheat systems are likely to become shorter due to advanced planting dates of rabi wheat, which implies that double-rice systems in the BIM countries will have more flexibility to cope with smaller time windows for crop growth and development in the future. Moreover, nearly half of the study area has the potential to increase yield by more than 10% through changing crop calendars compared to the basic scenario with non-adjusted crop calendars under RCP8.5 in 2080s, but 59% of these areas would face contradictions in obtaining crop yield improvement, saving irrigation water, and mitigating heat stress in the future. We found those areas suitable for adopting shifting planting dates as one of adaptation strategies from the perspective of climate conditions, such as Punjab state in India and Rangpur in Bangladesh, are also the areas with shortened growing season intervals, which requires great efforts to achieve the adaptation objectives under climate change. Thus, the trade-off among climate change adaptation, ecological sustainability, and farmer decision making should be carefully considered for local governments when promoting adjustment of crop calendars in rice-based multiple cropping systems.</p>