Journal
WATER
Volume 13, Issue 22, Pages -Publisher
MDPI
DOI: 10.3390/w13223235
Keywords
paddy field; rainfall; runoff; non-point source pollution; in-situ method
Categories
Funding
- Major Science and Technology Programme for Water Pollution Control and Treatment [2013ZX07501-005, 2017ZX07301-003]
- Fundamental Research Funds for the Central Universities
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A Beijing paddy field was used to validate and refine the in-situ observation method for describing nonpoint source pollution. The study found that the IO method was effective in estimating ET+F and NPS pollution, with small deviations observed in TN, TP, COD, NO3--N, and NH4+-N pollution loads. The location of water level gauges had little impact on IO but influenced water depth observations during the drying period.
A Beijing paddy field, along with in-situ experiments, was used to validate and refine the in-situ observation (IO) method to describe nonpoint source pollution (NPS) in paddy fields. Based on synchronous observed rainfall, water depth, and water quality data at two locations (1# (near inlet) and 2# (near outlet)) with large elevation differences, the evapotranspiration and infiltration loss (ET+F), runoff depth and NPS pollution load were calculated according to IO, and a common method was used to calculate ET+F. Then, the results of the different methods and locations were compared and analyzed. The results showed that 1# observation point was located at a lower position compared with 2# observation point. According to 1# observation point, there were 5 days of dry field in the drying period, which was consistent with the actual drying period, and there was a dry period of 9 days based on 2# observation point. The ET+F estimated by IO fit well with the calculated values. In the experiment, 6 overflows and 1 drainage event were identified from the observed data at locations 1# and 2#. The relative deviation of the NPS pollution of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), nitrate-nitrogen (NO3--N) and ammonia nitrogen (NH4+-N) was between 0.6% and 2.0%. The water level gauge location had little influence on IO but mostly affected the water depth observations during the field drying period. The mareographs should be installed in low-lying paddy field areas to monitor water depth variation throughout the whole rice-growing season.
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