Monitoring of Irrigation Schemes by Remote Sensing: Phenology versus Retrieval of Biophysical Variables

Abstract

Abstract:The appraisal of crop water requirements (CWR) is crucial for the management of water resources, especially in arid and semi-arid regions where irrigation represents the largest consumer of water, such as the Doukkala area, western Morocco. Simple and (semi) empirical approaches have been applied to estimate CWR: the first one is called K c -NDVI method, based on the correlation between the Normalized Difference Vegetation Index (NDVI) and the crop coefficient (K c ); the second one is the analytical approach based on the direct application of the Penman-Monteith equation with reflectance-based estimates of canopy biophysical variables, such as surface albedo (r), leaf area index (LAI) and crop height (h c ). A time series of high spatial resolution RapidEye (REIS), SPOT4 (HRVIR1) and Landsat 8 (OLI) images acquired during the 2012/2013 agricultural season has been used to assess the spatial and temporal variability of crop evapotranspiration ET c and biophysical variables. The validation using the dual crop coefficient approach (K cb 5816 adequacy between water requirements and allocations showed that CWR were much larger than allocated surface water for the entire area, with this difference being small at the beginning of the growing season. Even smaller differences were observed between surface water allocations and Irrigation Water Requirements (IWR) throughout the irrigation season. Finally, surface water allocations were rather close to Net Irrigation Water Requirements (NIWR).

Estimation of Evapotranspiration and Crop Coefficients of Tendone Vineyards Using Multi-Sensor Remote Sensing Data in a Mediterranean Environment

“…Since LAI represents the main parameter, it can be taken as the reference variable for the calibration of this method to local conditions, as described later. Recent studies conducted in semi-arid areas confirm this trend [50]; in fact, a percentage change of 50% in hc * corresponds to a variation of 5% of Kc. Therefore, a constant value of hc = 0.4 m has been set in this study, valid for the climatic conditions of the Mediterranean area, reducing the calculation to the estimation of r and LAI.…”

“…The effect of weighting the red band with the slope of the soil line is the maximization of the vegetation signal in the near-infrared band and the minimization of the effect of soil brightness. The LAI is related with WDVI of the observed vegetation, through the following expression, deduced from a simplified analysis of the radiative behavior of different types of crops [50,55,56]:…”

Temporal-Spatial Evolution Analysis of Lake Size-Distribution in the Middle and Lower Yangtze River Basin Using Landsat Imagery Data

“…In the dry season, the water is released down the river, and the reservoir level drops to prepare for the next flood. Dongting Lake, located in the area from 28°30′N to 30°20′N and from 112°25′E to 113°15′E, has a water storage capacity of approximately 17.8 billion· m 3 and plays an important role in flood storage. Its climate is mild and humid, and its MAAT (mean annual air temperature) is approximately 17° Celsius.…”

“…It is a major source of drinking and irrigation water for surrounding areas. Poyang Lake, located between 28°22′N and 29°45′N and between 115°47′E and 116°45′E, has a water storage volume of approximately 25 billion· m 3 . The annual inflow into Poyang Lake is about 16% of the annual runoff of the Yangtze River.…”

“…Under the influence of LUCC (Land-Use and Land-Cover Change) and other forms of environmental change, surface water, as one of the most important resources on Earth, has undergone constant temporal and spatial evolution. For many years, the impacts of surface water evolution on ecology, society, health and the economy have been topics of a large number of academic studies [3][4][5][6][7][8][9][10]. For example, the areas of 22 relatively large lakes in the southeast region of Qiangtang Plateau have been expanding during 30 years of increasing ice melt, snowmelt, and rainfall, and decreasing evaporation [11].…”