Paula Paredes

Estimation of Actual Crop Coefficients Using Remotely Sensed Vegetation Indices and Soil Water Balance Modelled Data

A new procedure is proposed for estimating actual basal crop coefficients from vegetation indices (Kcb VI) considering a density coefficient (Kd) and a crop coefficient for bare soil. Kd is computed using the fraction of ground cover by vegetation (fc VI), which is also estimated from vegetation indices derived from remote sensing. A combined approach for estimating actual crop coefficients from vegetation indices (Kc VI) is also proposed by integrating the Kcb VI with the soil evaporation coefficient (Ke) derived from the soil water balance model SIMDualKc. Results for maize, barley and an olive orchard have shown that the approaches for estimating both fc VI and Kcb VI compared well with results obtained using the SIMDualKc model after calibration with ground observation data. For the crops studied, the correlation coefficients relative to comparing the actual Kcb VI and Kc VI with actual Kcb and Kc obtained with SIMDualKc were larger than 0.73 and 0.71, respectively. The corresponding regression coefficients were close to 1.0. The methodology herein presented and discussed allowed for obtaining information for the whole crop season, including periods when vegetation cover is incomplete, as the initial and development stages. Results show that the proposed methods are adequate for supporting irrigation management.

SIMDualKc, A Software Tool for Water Balance Simulation Based on Dual Crop Coefficient

SIMDualKc is a software application for soil water balance simulation, based on the dual cropcoefficient (Kcb + Ke). The main goal of this software is to develop a tool to compute crop waterrequirements, particularly focused on vegetables and orchards, which have high irrigation frequencies andhave a fraction of the ground surface with bare soil during the irrigation season. This model was developedeither to operate alone carrying out all the computational procedures or to be integrated with other irrigationscheduling models, such as WINSAREG for the adoption of the dual Kc approach. In addition, this modelcan also be used to real-time irrigation scheduling, for assessing the evolution of the soil water content. TheSIMDualKc model was developed using a three tiers architecture approach. Thus, three differentcomponents were built: a graphic user interface (GUI), a mathematical model and a database. Thecomputational module was built to enable an easy integration with the WINISAREG model or to beoperated alone through the GUI. This feature was achieved using two abstract interfaces: one that links thecomputation module with the GUI or with a selected model; the other to perform the connection with thedifferent databases using queries. The data structure of this model, clearly separating the algorithmprocedures from the database, enables the connection of this application to different databases, including ageoreferenced database (GIS). This model was validated for the irrigation project of Fergana valley,Uzbequistan, showing a good adherence of model results to field observations.