Scale Effects on the Reduction of Drainage Water and Nitrogen and Phosphorus Loads in Hilly Irrigation Areas

The objectives of this study were to clarify the effects scale on farmland drainage water and nitrogen phosphorusload discharged in hilly irrigation areas. An experimental was conducted monitor volume phosphorus concentrations at field, lateral ditch (with a control area 1.16 km2), branch 7.76 watershed 43.3 km2) scales Yangshudang Zhanghe Irrigation District during rice growth period 2022. results showed that from field scale, water, total load, nitrate ammonia load per unit reduced by 74.6%, 88%, 85%, 87%, 60%, respectively. loads nitrogen, decreased with increase showing pronounced effect; however, infrequent recharge ponds weirs insufficient storage capacity ditches led an hence discharge instead, as study. effect mainly caused reuse water; thus, ability weirs, ditches, reservoirs areas regulate should be improved. methods have significant influence discharge. non-point sources focus controlling late tillering stage improving function above so pollutants.