Head ditch hydraulics and the variability of inflows to irrigation furrows

Abstract

The spatial variability and temporal variation of furrow inflows have a major impact on the performance of furrow irrigation, as indicated by the usual measures of application efficiency and uniformity. They also cause difficulties in determining the soil infiltration characteristic through inverse solution techniques and in selecting preferred values for the operational variables of flow rate and time to cut-off to give maximum performance at the field scale.In this paper a steady spatially-varied flow analyses is performed to predict the steady water surface profiles in a typical head ditch and the subsequent spatial variability of the furrow inflows, for both pipe or siphon and sill or bank-less type water application systems. The resulting patterns were very similar to those seen in the spatially varied pipe flow in gated pipe, with depths and outflows increasing toward the downstream end of the channel. It is shown that it is feasible to design head ditches to minimise the variability in outflows. An unsteady analysis of the same head ditch illustrated the variation of outflows with time caused by the time taken to fill the channel. AbstraitLa variabilité spatiale et la variation temporelle des apports de sillon ont un impact important sur l'exécution de l'irrigation de sillon, en termes de mesures habituelles d'efficacité et d'uniformité d'application. Elles également occasionnent des difficultés en déterminant les techniques inverses traversantes caractéristiques de solution d'infiltration de sol et en choisissant des valeurs préférées pour les variables opérationnelles du débit et temps-à-coupent-au loin pour donner l'exécution optima à la balance de champ.Des analyses de flux Spatial-changées sont exécutées pour prévoir les profils réguliers de surface de l'eau dans un fossé typique de tête d'irrigation. La variabilité spatiale suivante des apports de sillon est analysée, des types de siphon-et-filon-couche ou de banque-moins de systèmes d'application de l'eau. Les modèles résultants étaient très semblables à ceux vus dans spatial-changé pipe-coulent dans la pipe à déchenchements périodiques, avec des profondeurs et des sorties augmentant vers l'extrémité descendant du canal. On voit qu'il est faisable pour concevoir les fossés principaux pour réduire au minimum la variabilité dans les sorties. Une analyse perturbée du même tête-fossé a illustré la variation des sorties avec du temps causé avant que pris pour remplir canal.

Performance Evaluation of Field Water Application at Tendaho Sugar Estate, Ethiopia

“…The mean values critical flow has calculated as tabulated below at the existing slope of 0.05% (Table 9) [15].…”

Comparative Efficiency Analysis of Irrigation Scheme Categories of Awash River Basin, Ethiopia

“…FGP is aboveground pipe used for distributing water into furrow and can either be rigid or flexible. It is widely used because of its low cost and space to store as well as ease of transporting (Smith and Gillies 2009). According to Hassan (1998), it has made furrow system more efficient; easier to operate and maintain; can attain 35 to 60% water and labor cost reduction; provides uniform distribution into furrows; and reduce seepage and evaporative losses.…”

Assinaturas topográficas humanas (ATH´S) no contexto dos canais derivados multifuncionais e suas repercussões hidrogeomorfológicas

“…Este fato atesta a problemática separação entre homem e natureza, apontada por Haff (2003). Logo, tomando estudos sobre os canais artificiais e suas atribuições, tal como na transposição (NEWLIN, et al, 2002;ZETLAND, 2009), irrigação (PAUDYAL et al, 1991;GILLIES, 2010), drenagem (ABDEL-DAYEM e EL-SAFTY, 1993;BRADY et al 2014), é visível a pequena abrangência das pesquisas sobre o significado de suas formas para a alterações de condições ambientais.…”

“…(ex, SHAACK, 1986;PAUDYAl et al, 1991;SNELL, 2001;GILLIES, 2010). A eficácia na captação de água é fundamental por permitir a otimização do uso dos volumes disponíveis, (WOLTERS et al, 1987;RIJO;PEREIRA, 1987;RENAULT, 1988;MURRAY-RUST;VANDER VELDE, 1994), se direcionam esforços para o monitoramento das vazões e melhoria nas suas partilhas (ex, BHUTTA; VAN DER VELDE, 1992;REPLOGLE 1997;KOUCHAKZADEH;MARASHI, 2005;WAHL et al, 2005).…”