Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow
Understanding the coupled continuum pipe-flow framework for modeling contaminant transport in karst systems is critical for protecting water resources therein. This study simulated point and non-point source nitrate concentration in a karst spring and investigated the results generated from the flow...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-05-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/14/10/1622 |
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| author | Yuan Gao Zexuan Xu Shen Li Wenjie Yu |
| author_facet | Yuan Gao Zexuan Xu Shen Li Wenjie Yu |
| author_sort | Yuan Gao |
| collection | DOAJ |
| description | Understanding the coupled continuum pipe-flow framework for modeling contaminant transport in karst systems is critical for protecting water resources therein. This study simulated point and non-point source nitrate concentration in a karst spring and investigated the results generated from the flow and transport model with and without discrete conduit flow. CFPv2 and CMT3D models were integrated to address the changes in nitrate concentration at a monthly scale in a karst spring, and the results were compared with that from an equivalent porous media (EPM) model with high-hydraulic conductivity (K) zones set in the main karstified area to represent conduits. The results show that the CFPv2+CMT3D model is able to describe well the recession of nitrate concentration in spring discharge, and the relatively larger deviation (slower nitrate recession) from the observed trend for the EPM model is probably a result of the limitation of utilizing high hydraulic conductivity cells to represent conduit. Moreover, simulated hydraulic heads in poorly karstified areas from the two models both show slight differences from the observations (the head RMSE values of calibration/validation for CFPv2 and MODFLOW models are 0.16 m/0.25 m and 0.26 m/0.17 m, respectively), indicating the inclusion of conduits may not affect the simulation considerably, and the lower the proportion of karstic area, the slight effects brought from the inclusion of conduits in the model. For highly karstified areas, the CFPv2+CMT3D model could provide more accurate results (head RMSE of calibration/validation for CFPv2 and MODFLOW are 0.22 m/0.06 and 0.52 m/0.47 m, respectively), showing the coupled continuum pipe-flow framework may be more appropriate for applying to highly and maturely karstified areas where the variations in the behavior of flow and contaminant transport are more affected by turbulent flow regime. |
| first_indexed | 2024-03-10T01:34:16Z |
| format | Article |
| id | doaj.art-1ffbf36b802b45eaba8e583ff70e39a5 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T01:34:16Z |
| publishDate | 2022-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-1ffbf36b802b45eaba8e583ff70e39a52023-11-23T13:35:18ZengMDPI AGWater2073-44412022-05-011410162210.3390/w14101622Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit FlowYuan Gao0Zexuan Xu1Shen Li2Wenjie Yu3School of Geology and Mining Engineering, Xinjiang University, Urumqi 830017, ChinaEarth and Environmental Science Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USASchool of Geology and Mining Engineering, Xinjiang University, Urumqi 830017, ChinaSchool of Geology and Mining Engineering, Xinjiang University, Urumqi 830017, ChinaUnderstanding the coupled continuum pipe-flow framework for modeling contaminant transport in karst systems is critical for protecting water resources therein. This study simulated point and non-point source nitrate concentration in a karst spring and investigated the results generated from the flow and transport model with and without discrete conduit flow. CFPv2 and CMT3D models were integrated to address the changes in nitrate concentration at a monthly scale in a karst spring, and the results were compared with that from an equivalent porous media (EPM) model with high-hydraulic conductivity (K) zones set in the main karstified area to represent conduits. The results show that the CFPv2+CMT3D model is able to describe well the recession of nitrate concentration in spring discharge, and the relatively larger deviation (slower nitrate recession) from the observed trend for the EPM model is probably a result of the limitation of utilizing high hydraulic conductivity cells to represent conduit. Moreover, simulated hydraulic heads in poorly karstified areas from the two models both show slight differences from the observations (the head RMSE values of calibration/validation for CFPv2 and MODFLOW models are 0.16 m/0.25 m and 0.26 m/0.17 m, respectively), indicating the inclusion of conduits may not affect the simulation considerably, and the lower the proportion of karstic area, the slight effects brought from the inclusion of conduits in the model. For highly karstified areas, the CFPv2+CMT3D model could provide more accurate results (head RMSE of calibration/validation for CFPv2 and MODFLOW are 0.22 m/0.06 and 0.52 m/0.47 m, respectively), showing the coupled continuum pipe-flow framework may be more appropriate for applying to highly and maturely karstified areas where the variations in the behavior of flow and contaminant transport are more affected by turbulent flow regime.https://www.mdpi.com/2073-4441/14/10/1622karst aquiferconduit flow processnitratespring |
| spellingShingle | Yuan Gao Zexuan Xu Shen Li Wenjie Yu Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow Water karst aquifer conduit flow process nitrate spring |
| title | Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow |
| title_full | Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow |
| title_fullStr | Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow |
| title_full_unstemmed | Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow |
| title_short | Modeling Monthly Nitrate Concentration in a Karst Spring with and without Discrete Conduit Flow |
| title_sort | modeling monthly nitrate concentration in a karst spring with and without discrete conduit flow |
| topic | karst aquifer conduit flow process nitrate spring |
| url | https://www.mdpi.com/2073-4441/14/10/1622 |
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