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spec: " This means that on both sides of the Rio Grande , irrigation districts must line their larger canals , substitute small canals with pipe systems , and on-farm irrigation has to be improved by replacing ditches with flexible plastic pipes , often called poly pipe , and improve water management practices to reduce runoff and deep percolation . Their research has helped establish management practices to reduce plant-related losses . This defines the overall title of the entire document . Each dial has a pair of radial lines with handles at their ends . Practica geometriae , published in 1220 , contained a large collection of geometry problems , based in large part on Euclid 's Elements , together with a lot of practical trigonometric problems aimed at surveyors . Water Quality - Improved field and watershed management practices to reduce chemical concentrations in surface runoff .