Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
11,310
result(s) for
"Water requirements"
Sort by:
Remote Sensing for Crop Water Management: From ET Modelling to Services for the End Users
The experiences gathered during the past 30 years support the operational use of irrigation scheduling based on frequent multi-spectral image data. Currently, the operational use of dense time series of multispectral imagery at high spatial resolution makes monitoring of crop biophysical parameters feasible, capturing crop water use across the growing season, with suitable temporal and spatial resolutions. These achievements, and the availability of accurate forecasting of meteorological data, allow for precise predictions of crop water requirements with unprecedented spatial resolution. This information is greatly appreciated by the end users, i.e., professional farmers or decision-makers, and can be provided in an easy-to-use manner and in near-real-time by using the improvements achieved in web-GIS methodologies (Geographic Information Systems based on web technologies). This paper reviews the most operational and explored methods based on optical remote sensing for the assessment of crop water requirements, identifying strengths and weaknesses and proposing alternatives to advance towards full operational application of this methodology. In addition, we provide a general overview of the tools, which facilitates co-creation and collaboration with stakeholders, paying special attention to these approaches based on web-GIS tools.
Journal Article
Major crops and water scarcity in Egypt : irrigation water management under changing climate
Including multi-disciplinary quantifications of the effect of climate change on the water requirements of wheat, maize, rice and sugarcane, this text provides on-farm management that faces water scarcity under current situations and under climate change.
Book
Irrigation Scheduling for Maize under Different Hydrological Years in Heilongjiang Province, China
Appropriate irrigation schedules could minimize the existing imbalance between agricultural water supply and crop water requirements (ETc), which is severely impacted by climate change. In this study, different hydrological years (a wet year, normal year, dry year, and an extremely dry year) in Heilongjiang Province were calculated by hydrological frequency methods. Then, the single crop coefficient method was used to calculate the maize ETc, based on the daily meteorological data of 26 meteorological stations in Heilongjiang Province from 1960 to 2020. Afterward, the CROPWAT model was used to calculate the effective precipitation (Pe) and irrigation water requirement (Ir), and formulate the irrigation schedules of maize in Heilongjiang Province under different hydrological years. The results showed that ETc and Ir decreased first and then increased from west to east. The Pe and crop water surplus deficit index increased first and then decreased from west to east in Heilongjiang Province. Meanwhile, the average values of the Ir in were 171.14 mm, 232.79 mm, 279.08 mm, and 334.47 mm in the wet year, normal year, dry year, and extremely dry year, respectively. Heilongjiang Province was divided into four irrigation zones according to the Ir of different hydrological years. Last, the irrigation quotas for the wet year, normal year, dry year, and extremely dry year were 0~180 mm, 20~240 mm, 60~300 mm, and 80~430 mm, respectively. This study provides reliable support for maize irrigation practices in Heilongjiang Province, China.
Journal Article
Spatiotemporal variation of irrigation water requirements for grain crops under climate change in Northwest China
Clarifying the spatiotemporal variation of crop irrigation water requirement (IWR) under the background of climate change is an essential basis for water resource management, determining the irrigation quota and adjusting the planting structure. Using 61 years of climate data from 205 stations in Northwest China, this study investigated the spatiotemporal variations of climatic factors and IWR during the growth period of five main grain crops (spring wheat, winter wheat, spring maize, summer maize, and rice) and explored the dominant climatic driving factors of IWR variation. Results showed that (1) the IWR of grain crops showed distinct differences. Rice was the highest water consumption crop (mean of 753.78 mm), and summer maize was the lowest (mean of 452.90 mm). (2) The variation trends and average values of IWR of different grain crops have spatial heterogeneity across Northwest China. For most crops, high values and increasing trends of IWR were mainly located in eastern Xinjiang, western Gansu, and western Inner Mongolia. (3)
T
max
(maximum temperature),
T
min
(minimum temperature), and
P
eff
(effective precipitation) showed an increasing trend during the growth period of each grain crop, while
U
10
(wind speed at 10 m height), SD (solar radiation), and RH (relative humidity) presented decreasing trends. (4) SD,
T
max
, and
U
10
promoted the increase of grain crops’ IWR, while
P
eff
and RH inhibited it. The impacts of climatic factors on the grain crop IWR differed among different regions.
P
eff
was the most influential factor to the IWR of all grain crops in most areas. Therefore, under the premise of a significant increase in
T
and uncertain precipitation mode in the future, it is urgent to take effective water-saving measures according to the irrigation needs of the region. To cope with the adverse impact of climate change on the sustainable development of agriculture in the northwest dry area, to ensure regional and national food security.
Journal Article
Estimation of regional farmland irrigation water requirements and water balance in Northeast China
Agricultural water use has long accounted for more than 70% of water consumption in Northeast China. Estimating farmland irrigation water requirements and water balance is essential to ensure safe agricultural water and promote rational development and utilization of regional water resources. In this study, based on the modified Penman–Monteith equation recommended by the Food and Agriculture Organization (FAO) and Geographic Information System (GIS) technology, the net crop irrigation water requirements for four main crops in Northeast China were calculated, and the spatiotemporal distribution characteristics were also analyzed. Additionally, regional farmland irrigation water requirements were estimated, water balance in a typical year was determined, and the dominant factors affecting farmland irrigation water requirements in different regions were analyzed. From 1986 to 2020, the net irrigation water requirements for four main crops all showed the temporal trend of no significant increase and the spatial distribution characteristic of being high in the west and low in the east. The farmland irrigation water requirement decreased, and the monthly average farmland irrigation water requirement peaked in July during 2010–2019. Compared with 2010, in 2019, the irrigation water requirement per cultivated land grid cell in 20 cities increased and that in 16 cities decreased. Most cities were facing varying degrees of water shortage. Precipitation had the greatest direct effect on the farmland irrigation water requirement in different regions. These results quantify the farmland irrigation water requirement and water balance in Northeast China, and provide a reference for water resources and related environmental governance.
Journal Article
Origin and assessment of groundwater pollution and associated health risk: a case study in an industrial park, northwest China
Groundwater quality which relates closely to human health has become as important as its quantity due to the demand for safe water. In the present study, an entropy-weighted fuzzy water quality index (WQI) has been proposed for performing groundwater quality assessment in and around an industrial park, northwest China, where domestic water requirements are solely met by groundwater. The human health risk was assessed with the model recommended by the United States Environmental Protection Agency. In addition, the sources of major ions and main contaminants were also analyzed. The study shows that groundwater in the study area has been contaminated conjunctively by natural processes and industrial and agricultural activities. Nitrate, manganese (Mn), fluoride, total dissolved solids, total hardness and sulfate are major contaminants influencing groundwater quality. Nitrate and heavy metals such as Mn are mainly affected by human agricultural activities and industrial production, while other contaminants are mainly originated from mineral weathering and water–rock interactions. The results of water quality assessment suggest that half of the groundwater samples collected are of medium quality thus require pretreatment before human consumption. The mean health risk caused by the consumption of contaminated groundwater in the area is 8.42 × 10⁻⁵ per year which surpasses the maximum acceptable level (5 × 10⁻⁵ per year) recommended by the International Commission on Radiologic Protection. The entropy-weighted fuzzy WQI proposed in this study can not only assign proper weights to parameters but also treat uncertainties associated with water quality classification. This study will be of interest to international environmentalists and hydrogeologists. It will also be useful in regional groundwater management and protection.
Journal Article
Assessing recent impacts of climate change on design water requirement of Boro rice season in Bangladesh
Water requirement is sensitive to the impacts of climate change, especially in Bangladesh because of limited freshwater availability in the dry season, despite the fact that the country’s agriculture sector requires large quantities of water for the crop production. Hence, gaining a better understanding of changes in water requirements in Bangladesh during dry periods is important in the management of agricultural water resources. This study assesses the recent impacts of climate change on the design water requirement (DWR) of the Boro rice–growing season in Bangladesh using a frequency analysis over a 5-year period. The reference evapotranspiration (ETref), crop evapotranspiration (ETp), effective rainfall (ERF), and gross irrigation water requirements (GIWR) of Boro rice were estimated based on daily weather data for the period of 1984–2013 using the CROPWAT8.0 model. The results showed the significant decreasing trends of ETref in most of these Boro rice growth stages in all districts. The GIWR of Boro rice and its trends demonstrated significant spatial heterogeneity in the last three decades due to significant changes in the ERF and ETp. The DWR of Boro rice–growing season also supported the results of the GIWR, and the Weibull probability distribution function (PDF) is found to be an optimal PDF among eight PDFs for the estimation of DWR. Overall, the results indicate that a recent climate change does not only contribute to high water demands for the crop but also result in decrease water requirements due to variations in wind speed, sunshine hours, and relative humidity.
Journal Article
CLMcrop yields and water requirements: avoided impacts by choosing RCP 4.5 over 8.5
We perform CLMcrop simulations of the 20th and 21st centuries to assess potential avoided impacts in (a) crop yield losses and (b) water demand increases if humanity were to choose the representative concentration pathway (RCP) 4.5 instead of 8.5. RCP 8.5 imposes more extreme climatic changes on CLMcrop, while simultaneously exposing the crops to higher CO2 fertilization than RCP 4.5. As a result CLMcrop simulates global to regional scale changes in yield and water requirements for RCP 8.5 that exceed and sometimes more than double the RCP 4.5 changes relative to today. Under RCP 4.5 then, human societies may confront easier adaptation to changes in crop yields and water requirements. Under both RCPs, CLMcrop projects declining global yields for C3 crops (e.g., wheat, soybean, rice) without CO2 fertilization and C4 crops (corn, sugarcane) without irrigation. Yield declines of 3 t ha−1 stand out in parts of tropical and subtropical Africa and South America (presently areas of rapid agricultural expansion) and are due to increasing plant respiration and decreasing soil moisture, both due to rising temperatures. Irrigation and CO2 fertilization mitigate yield losses and in some cases lead to gains, so irrigation may help maintain or increase current yields through the 21st century. However, simulated global irrigation requirements increase: as much as 23 % for C4 crops without CO2 fertilization under RCP 8.5 and as little as 3 % for C4 crops with CO2 fertilization under RCP4.5. Nitrogen fertilized crops display greater vulnerability to climate and environmental change than unfertilized crops in our simulations; still relative to unfertilized crops, they deliver significantly higher yields and remain indispensable in supporting a more populous and affluent humanity. These CLMcrop results broadly agree with previously published outcomes for the 21st century. We describe in this article a new version of CLMcrop that represents prognostic crop behavior not only in the mid-latitudes but also the tropics.
Journal Article
Impacts of planting structure adjustment on water saving in the Shiyang River Basin of Arid Region
Planting structure adjustment (PSA) affects agricultural water saving, and is an essential part of water-saving agricultural construction. This study introduced virtual water theory and innovatively constructed a model to assess the water-saving effects of PSA in Shiyang River Basin over the past 38 years, explore the relationship between planting structure and water saving, and clarify the most water-saving planting structure. The results showed that the sown area of economic crops consistently increased as food crop areas decreased in the four counties (districts) from 1980 to 2017. Being considered a “big water consumer”, wheat has lost its dominant position. The water requirements of major crops in the four counties and districts showed an increasing trend. The total area proportion of vegetables, wheat, corn, and oil-bearing crops (Abbreviated as TPVWCO) directly determined the water-saving amount. The lower the TPVWCO, the better the water-saving effect. Taking 1980 as the reference year, the most water-saving years in Gulang, Liangzhou, Yongchang, and Minqin were 2007, 1981, 2008, and 2005, respectively. Taking 2007 as the reference year, there were no water-saving years available after that due to the higher TPVWCO. Taking into account food security, ecological and economic benefits, it was recommended to control the TPVWCO at 40% in the Shiyang River Basin in the future. The land vacated should be planted with cotton in Minqin, while the land vacated in the other three counties should be planted with fruits. The research results would provide scientific basis for optimizing the planting structure and managing agricultural water resources in inland river basins in arid regions.
Journal Article