Synoptic Sampling to Determine Distributed Groundwater-Surface Water Nitrate Loading and Removal Potential Along a Lowland River
Pai, H; Villamizar, SR; Harmon, TC
| HERO ID | 8036314 |
|---|---|
| In Press | No |
| Year | 2017 |
| Title | Synoptic Sampling to Determine Distributed Groundwater-Surface Water Nitrate Loading and Removal Potential Along a Lowland River |
| Authors | Pai, H; Villamizar, SR; Harmon, TC |
| Journal | Water Resources Research |
| Volume | 53 |
| Issue | 11 |
| Page Numbers | 9479-9495 |
| Abstract | Delineating pollutant reactive transport pathways that connect local land use patterns to surface water is an important goal. This work illustrates high-resolution river mapping of salinity or specific conductance (SC) and nitrate (NO3-) as a potential part of achieving this goal. We observed longitudinal river SC and nitrate distributions using high-resolution synoptic in situ sensing along the lower Merced River (38 river km) in Central California (USA) from 2010 to 2012. We calibrated a distributed groundwater-surface water (GW-SW) discharge model for a conservative solute using 13 synoptic SC sampling events at flows ranging from 1.3 to 31.6 m(3) s(-1). Nitrogen loads ranged from 0.3 to 1.6 kg N d(-1) and were greater following an extended high flow period during a wet winter. Applying the distributed GW-SW discharge estimates to a simplistic reactive nitrate transport model, the model reproduced observed river nitrate distribution well (RRMSE=5-21%), with dimensionless watershed-averaged nitrate removal (kt) ranging from 0 to 0.43. Estimates were uncertain due to GW nitrate data variability, but the resulting range was consistent with prior removal estimates. At the segment scale, estimated GW-SW nitrate loading ranged from 0 to 17 g NO3- s(-1) km(-1). Local loading peaked near the middle of the study reach, a location that coincides with a shallow clay lens and with confined animal feed operations in close proximity to the river. Overall, the results demonstrate the potential for high-resolution synoptic monitoring to support GW-SW modeling efforts aimed at understanding and managing nonpoint source pollution. |
| Doi | 10.1002/2017WR020677 |
| Wosid | WOS:000418736700045 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Keyword | nitrate; river |