Canal Geometry, Flow Velocity, Dallisgrass (Paspalum dilatatum Poir.) Density and Soil Phosphorous Effects on Hydraulic Resistance of Vegetated Canals

Abstract

Dallisgrass Paspalum dilatatum Poir. reduces discharges in irrigation canals and causes problems in operation and maintenance of canals. This study has been conducted to determine roughness coefficient in vegetated canals caused by dallisgrass and to investigate the relationship between available soil phosphorous and dry mass of dallisgrass. The study also aims to find out the relationships among roughness coefficient, dallisgrass density and soil phosphorous in vegetated canals in Moghan plain, Iran. The results showed that the roughness coefficient varied from 0.01 to 0.32 and averaged at 0.09. The variation in roughness coefficient in vegetated canals by dallisgrass may be explained solely by the flow velocity and canal slope, assuming that there are no spatial variability’s of the other affecting variables. Therefore, a regression model comprises both the roughness coefficient as a dependent variable and the flow velocity and canal slope as an independent variable is developed. The available soil phosphorus both on the sides and at the bottom of vegetated canals were from 4.2 to 37 mg kg-1. The highest dry mass of 16 kg per 100 m2 was acquired from the canal with soil phosphorus of 16.7 mg kg-1. Also, another model was developed to describe the roughness coefficient as a function of the flow velocity, canal slope, dallisgrass density and soil phosphorous. It is recommended that identifying phosphorus sources and limiting its distribution in irrigation canals is necessary to reduce the dallisgrass density in canals

Keywords

• Available soil phosphorous
• Dallisgrass Paspalum dilatatum Poir.
• Hydraulic resistance
• Irrigation canals
• Roughness coefficient

Otlanmış Kanallarda Kanal Geometrisi, Akış Hızı, Adi Yalancı Darı Paspalum dilatatum Poir. Yoğunluğu ve Toprak Fosfor Oranının Hidrolik Direnç Üzerine Etkisi

Abstract

Adi yalancı darı Paspalum dilatatum Poir. sulama kanallarında akışı azaltmakta ve işletme-bakım sorunlarına neden olmaktadır. Bu çalışma, otlanmış kanallarda Adi yalancı darı’nın pürüzlülük katsayısını nasıl etkilediğini ve topraktaki mevcut fosfor ile adi yalancı darı kuru ağırlığı arasındaki ilişkiyi araştırmak amacıyla yapılmıştır. Ayrıca; çalışma İran’da Mogan ovasında bulunan otlanmış kanallardaki pürüzlülük katsayısı ile adi yalancı darı yoğunluğu ve topraktaki mevcut fosfor miktarı arasındaki ilişkiyi belirlemeyi de amaçlamaktadır. Araştırma sonucunda; pürüzlülük katsayısı değerleri 0.01-0.032 arasında değişmiş ve ortalama olarak 0.09 olarak bulunmuştur. Diğer değişkenlerin olmadığı varsayıldığında, adi yalancı darı ile otlanmış kanallardaki pürüzlülük katsayısı değişkenlerini, sadece akış hızı ve kanal eğiminin etkilediği söylenebilir. Bu nedenle; bağımlı değişken olarak pürüzlülük katsayısını, bağımsız değişken olarak da akış hızı ve kanal eğimini kapsayan regresyon modeli geliştirilmiştir. Otlanmış kanalların kenarlarında ve tabanındaki mevcut fosfor miktarı 4.2’den 37 mg kg-1’e kadar yükselmiştir. En yüksek kuru madde miktarı 16.7 mg kg-1 fosfora sahip kanaldan 100 m2’ye 16 kg olarak elde edilmiştir. Ayrıca, akış hızı fonksiyonu, kanal eğimi, adi yalancı darı yoğunluğu ve mevcut toprak fosforunu pürüzlülük katsayısı olarak tanımlayan başka bir model de geliştirilmiştir. Sonuç olarak; kanallardaki adi yalancı darı yoğunluğunu azaltmak için fosfor kaynaklarının belirlenmesi ve sulama kanallarının dağılımının sınırlandırılmasının gerekli olduğu önerilmektedir

Keywords

• Yarayışlı toprak fosforu
• Adi yalancı darı Paspalum dilatatum Poir.
• Hidrolik direnç
• Sulama kanalları
• Pürüzlülük katsayısı

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