https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&feed=atom&action=history
Interpreting wasteload allocations based on flow/load duration curves - Revision history
2024-03-28T18:47:13Z
Revision history for this page on the wiki
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https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=63285&oldid=prev
Mtrojan: /* Suggested reading */
2022-12-03T15:23:47Z
<p><span dir="auto"><span class="autocomment">Suggested reading</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 15:23, 3 December 2022</td>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://pubs.usgs.gov/wsp/1542a/report.pdf Flow-Duration Curves, James K. Searcy, Manual of Hydrology: Part 2. Low-Flow Techniques] (GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1542-A)</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://pubs.usgs.gov/wsp/1542a/report.pdf Flow-Duration Curves, James K. Searcy, Manual of Hydrology: Part 2. Low-Flow Techniques] (GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1542-A)</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://www.sciencedirect.com/topics/engineering/flow-duration-curve Flow duration curves]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://www.sciencedirect.com/topics/engineering/flow-duration-curve Flow duration curves]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Category:Level 3 - Regulatory/Municipal (MS4)/TMDLs]]</ins></div></td></tr>
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Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=49211&oldid=prev
Mtrojan at 18:17, 19 May 2020
2020-05-19T18:17:08Z
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 18:17, 19 May 2020</td>
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<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">{{alert|This page is under review during the MS4 Phase 2 permit reissuance period|alert-under-review}}</del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;"></del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Flow duration curve.png|300px|thumb|alt=image of flow duration curve|<font size=3>Example of a flow duration curve ([https://pubs.usgs.gov/wsp/1542a/report.pdf Searcy, 1959]</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Flow duration curve.png|300px|thumb|alt=image of flow duration curve|<font size=3>Example of a flow duration curve ([https://pubs.usgs.gov/wsp/1542a/report.pdf Searcy, 1959]</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td></tr>
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Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=46814&oldid=prev
Mtrojan at 21:35, 11 February 2020
2020-02-11T21:35:50Z
<p></p>
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 21:35, 11 February 2020</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l35" >Line 35:</td>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The above recommendation does not apply for bacteria TMDLs, since bacteria concentrations in stormwater runoff and receiving waters are typically greatest under wet weather conditions. Stormwater management for bacteria should therefore focus on wet weather conditions, which typically are correlated with higher flow conditions in receiving waters.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The above recommendation does not apply for bacteria TMDLs, since bacteria concentrations in stormwater runoff and receiving waters are typically greatest under wet weather conditions. Stormwater management for bacteria should therefore focus on wet weather conditions, which typically are correlated with higher flow conditions in receiving waters.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">{{alert|Do not apply the recommendation discussed above to TMDLs for bacteria|alert-warning}}</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Suggested reading==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Suggested reading==</div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=46806&oldid=prev
Mtrojan at 20:22, 7 February 2020
2020-02-07T20:22:59Z
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 20:22, 7 February 2020</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l21" >Line 21:</td>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Jordan River flows.png|300px|thumb|alt=MN River flows|<font size=3>Monthly Minnesota River discharge at Jordan, 2011-2019. ([https://snoflo.org/report/flow/minnesota/minnesota-river-near-jordan/almanac/ Source])</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Jordan River flows.png|300px|thumb|alt=MN River flows|<font size=3>Monthly Minnesota River discharge at Jordan, 2011-2019. ([https://snoflo.org/report/flow/minnesota/minnesota-river-near-jordan/almanac/ Source])</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For most <ins class="diffchange diffchange-inline">total suspended solids (TSS) </ins>TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Justification for this is based on the following.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Justification for this is based on the following.</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*Exceedances of water quality criteria occur only at low and/or very low flows. In this case, the permittee should apply the WLA for these flow regimes.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*Exceedances of water quality criteria occur only at low and/or very low flows. In this case, the permittee should apply the WLA for these flow regimes.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*The permittee has conducted appropriate modeling to account for load reductions at high or very high flow conditions.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*The permittee has conducted appropriate modeling to account for load reductions at high or very high flow conditions.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The above recommendation does not apply for bacteria TMDLs, since bacteria concentrations in stormwater runoff and receiving waters are typically greatest under wet weather conditions. Stormwater management for bacteria should therefore focus on wet weather conditions, which typically are correlated with higher flow conditions in receiving waters.</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Suggested reading==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Suggested reading==</div></td></tr>
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Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=46805&oldid=prev
Mtrojan at 20:19, 7 February 2020
2020-02-07T20:19:19Z
<p></p>
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 20:19, 7 February 2020</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l4" >Line 4:</td>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{alert|When considering TMDLs based on load duration curves, the MPCA recommends using the mid value when determining wasteload allocations for MS4 permits. However, if your required pollutant reduction is zero (0) at the mid value we recommend contacting the Minnesota Pollution Control Agency for guidance. A required reduction of zero (0) at the mid value does not necessarily equate to no required actions if there are required reductions at other flow ranges,|alert-info}}</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{alert|When considering <ins class="diffchange diffchange-inline">Total suspended solids (TSS) or turbidity </ins>TMDLs based on load duration curves, the MPCA recommends using the mid value when determining wasteload allocations for MS4 permits. However, if your required pollutant reduction is zero (0) at the mid value we recommend contacting the Minnesota Pollution Control Agency for guidance. A required reduction of zero (0) at the mid value does not necessarily equate to no required actions if there are required reductions at other flow ranges,|alert-info}}</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Flow duration curves use historical records to relate flow values in a stream or river to the percent of time those values have been met or exceeded. The curves show flow from high to low along the Y-axis and the percent of time when that flow is exceeded on the X-axis. Flow duration curves are often divided into different flow regimes. For example, a curve could be divided into 3 regimes based on percent likelihood of exceedance. The three regimes could each account for 33.3 percent of the curve and be labeled as low, medium, and high flow regimes. Low flows are exceeded a majority of the time, while high flows are exceeded infrequently.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Flow duration curves use historical records to relate flow values in a stream or river to the percent of time those values have been met or exceeded. The curves show flow from high to low along the Y-axis and the percent of time when that flow is exceeded on the X-axis. Flow duration curves are often divided into different flow regimes. For example, a curve could be divided into 3 regimes based on percent likelihood of exceedance. The three regimes could each account for 33.3 percent of the curve and be labeled as low, medium, and high flow regimes. Low flows are exceeded a majority of the time, while high flows are exceeded infrequently.</div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=46799&oldid=prev
Mtrojan at 14:56, 7 February 2020
2020-02-07T14:56:08Z
<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 14:56, 7 February 2020</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l4" >Line 4:</td>
<td colspan="2" class="diff-lineno">Line 4:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Load duration curve.png|300px|thumb|alt=image load duration curve|<font size=3>TSS load duration curve for Buffalo Creek in Minnesota. From [https://www.pca.state.mn.us/sites/default/files/wq-iw8-52e.pdf South Fork Crow River Watershed Total Maximum Daily Load Report]</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{alert|When considering TMDLs based on load duration curves, the MPCA recommends using the mid value when determining wasteload allocations for MS4 permits|alert-info}}</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{alert|When considering TMDLs based on load duration curves, the MPCA recommends using the mid value when determining wasteload allocations for MS4 permits<ins class="diffchange diffchange-inline">. However, if your required pollutant reduction is zero (0) at the mid value we recommend contacting the Minnesota Pollution Control Agency for guidance. A required reduction of zero (0) at the mid value does not necessarily equate to no required actions if there are required reductions at other flow ranges,</ins>|alert-info}}</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Flow duration curves use historical records to relate flow values in a stream or river to the percent of time those values have been met or exceeded. The curves show flow from high to low along the Y-axis and the percent of time when that flow is exceeded on the X-axis. Flow duration curves are often divided into different flow regimes. For example, a curve could be divided into 3 regimes based on percent likelihood of exceedance. The three regimes could each account for 33.3 percent of the curve and be labeled as low, medium, and high flow regimes. Low flows are exceeded a majority of the time, while high flows are exceeded infrequently.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Flow duration curves use historical records to relate flow values in a stream or river to the percent of time those values have been met or exceeded. The curves show flow from high to low along the Y-axis and the percent of time when that flow is exceeded on the X-axis. Flow duration curves are often divided into different flow regimes. For example, a curve could be divided into 3 regimes based on percent likelihood of exceedance. The three regimes could each account for 33.3 percent of the curve and be labeled as low, medium, and high flow regimes. Low flows are exceeded a majority of the time, while high flows are exceeded infrequently.</div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=46074&oldid=prev
Mtrojan at 13:20, 13 November 2019
2019-11-13T13:20:33Z
<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 13:20, 13 November 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{alert|This page is under review|alert-under-review}}</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{alert|This page is under review <ins class="diffchange diffchange-inline">during the MS4 Phase 2 permit reissuance period</ins>|alert-under-review}}</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Flow duration curve.png|300px|thumb|alt=image of flow duration curve|<font size=3>Example of a flow duration curve ([https://pubs.usgs.gov/wsp/1542a/report.pdf Searcy, 1959]</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Flow duration curve.png|300px|thumb|alt=image of flow duration curve|<font size=3>Example of a flow duration curve ([https://pubs.usgs.gov/wsp/1542a/report.pdf Searcy, 1959]</font size>]]</div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=45788&oldid=prev
Mtrojan at 19:53, 31 October 2019
2019-10-31T19:53:11Z
<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 19:53, 31 October 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l19" >Line 19:</td>
<td colspan="2" class="diff-lineno">Line 19:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Recommendation for interpreting load duration curves for MS4 permittees==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Recommendation for interpreting load duration curves for MS4 permittees==</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File:Jordan River flows.png|300px|thumb|alt=MN River flows|<font size=3>Monthly Minnesota River discharge at Jordan, 2011-2019. ([https://snoflo.org/report/flow/minnesota/minnesota-river-near-jordan/almanac/ Source]</font size>]]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:Jordan River flows.png|300px|thumb|alt=MN River flows|<font size=3>Monthly Minnesota River discharge at Jordan, 2011-2019. ([https://snoflo.org/report/flow/minnesota/minnesota-river-near-jordan/almanac/ Source]<ins class="diffchange diffchange-inline">)</ins></font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=45786&oldid=prev
Mtrojan at 19:52, 31 October 2019
2019-10-31T19:52:51Z
<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 19:52, 31 October 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l19" >Line 19:</td>
<td colspan="2" class="diff-lineno">Line 19:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Recommendation for interpreting load duration curves for MS4 permittees==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Recommendation for interpreting load duration curves for MS4 permittees==</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File:<del class="diffchange diffchange-inline">Hydrograph</del>.<del class="diffchange diffchange-inline">gif</del>|300px|thumb|alt=<del class="diffchange diffchange-inline">hydrograph</del>|<font size=3><del class="diffchange diffchange-inline">Example of a stream hydrograph showing the contribution of overland flow</del>, <del class="diffchange diffchange-inline">throughflow, and baseflow </del>([<del class="diffchange diffchange-inline">http</del>://<del class="diffchange diffchange-inline">www.bbc.co</del>.<del class="diffchange diffchange-inline">uk</del>/<del class="diffchange diffchange-inline">scotland</del>/<del class="diffchange diffchange-inline">education/int</del>/<del class="diffchange diffchange-inline">geog</del>/<del class="diffchange diffchange-inline">rivers</del>/<del class="diffchange diffchange-inline">hydrographs</del>/ <del class="diffchange diffchange-inline">BBC</del>]<del class="diffchange diffchange-inline">).</del></font size>]]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:<ins class="diffchange diffchange-inline">Jordan River flows</ins>.<ins class="diffchange diffchange-inline">png</ins>|300px|thumb|alt=<ins class="diffchange diffchange-inline">MN River flows</ins>|<font size=3><ins class="diffchange diffchange-inline">Monthly Minnesota River discharge at Jordan</ins>, <ins class="diffchange diffchange-inline">2011-2019. </ins>([<ins class="diffchange diffchange-inline">https</ins>://<ins class="diffchange diffchange-inline">snoflo</ins>.<ins class="diffchange diffchange-inline">org</ins>/<ins class="diffchange diffchange-inline">report</ins>/<ins class="diffchange diffchange-inline">flow</ins>/<ins class="diffchange diffchange-inline">minnesota</ins>/<ins class="diffchange diffchange-inline">minnesota-river-near-jordan</ins>/<ins class="diffchange diffchange-inline">almanac</ins>/ <ins class="diffchange diffchange-inline">Source</ins>]</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs based on load duration curves, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value WLA when assessing compliance with or progress toward meeting a WLA, as specified in the MS4 General Permit. </div></td></tr>
</table>
Mtrojan
https://stormwater.pca.state.mn.us/index.php?title=Interpreting_wasteload_allocations_based_on_flow/load_duration_curves&diff=45782&oldid=prev
Mtrojan at 19:42, 31 October 2019
2019-10-31T19:42:58Z
<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-marker" />
<col class="diff-content" />
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<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 19:42, 31 October 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l21" >Line 21:</td>
<td colspan="2" class="diff-lineno">Line 21:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Hydrograph.gif|300px|thumb|alt=hydrograph|<font size=3>Example of a stream hydrograph showing the contribution of overland flow, throughflow, and baseflow ([http://www.bbc.co.uk/scotland/education/int/geog/rivers/hydrographs/ BBC]).</font size>]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Hydrograph.gif|300px|thumb|alt=hydrograph|<font size=3>Example of a stream hydrograph showing the contribution of overland flow, throughflow, and baseflow ([http://www.bbc.co.uk/scotland/education/int/geog/rivers/hydrographs/ BBC]).</font size>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value <del class="diffchange diffchange-inline">for </del>the <del class="diffchange diffchange-inline">WLA</del>. Justification for this is based on the following.</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For most TMDLs <ins class="diffchange diffchange-inline">based on load duration curves</ins>, the Minnesota Pollution Control Agency (MPCA) recommends using the mid value <ins class="diffchange diffchange-inline">WLA when assessing compliance with or progress toward meeting a WLA, as specified in </ins>the <ins class="diffchange diffchange-inline">MS4 General Permit</ins>. </div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>#'''TSS WLAs are underallocated for MS4 stormwater'''. In- and near-stream erosion processes typically dominate pollutant loading at high and very high flows. Stormwater practices that retain water on the landscape (e.g infiltration) or slow the release of runoff (e.g. constructed ponds and wetlands, many filtration practices) reduce erosion associated with in- and near-stream processes. These effects are not accounted for in load determinations (e.g. models) when setting TMDLs. Consequently, these practices are not properly credited at high and very high flows.</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Justification for this is based on the following.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#'''TSS WLAs are underallocated for MS4 stormwater'''. In- and near-stream erosion processes typically dominate pollutant loading at high and very high flows. Stormwater practices that retain water on the landscape (e.g infiltration) or slow the release of runoff (e.g. constructed ponds and wetlands, many filtration practices) reduce erosion associated with in- and near-stream processes. These effects are not accounted for in load determinations (e.g. models) when setting TMDLs. Consequently, these practices are not properly credited <ins class="diffchange diffchange-inline">for MS4s </ins>at high and very high flows.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#'''Stormwater practices are already most effective at times when high and very high flow occurs'''. The adjacent image shows that stream hydrographs typically show a lag of several hours to more than a day before achieving peak flow. In the absence of very large rainfall events, sustaining peak flows at high and very high levels requires extended periods of rainfall or snowmelt. For these extended periods of rainfall and snowmelt, BMPs designed to treat an instantaneous volume will typically be overdesigned and thus under-credited since they will release water gradually (e.g. through infiltration), resulting in increased capture of runoff.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#'''Stormwater practices are already most effective at times when high and very high flow occurs'''. The adjacent image shows that stream hydrographs typically show a lag of several hours to more than a day before achieving peak flow. In the absence of very large rainfall events, sustaining peak flows at high and very high levels requires extended periods of rainfall or snowmelt. For these extended periods of rainfall and snowmelt, BMPs designed to treat an instantaneous volume will typically be overdesigned and thus under-credited since they will release water gradually (e.g. through infiltration), resulting in increased capture of runoff.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#'''Stormwater BMP effectiveness decreases at times when stream flows are decreasing'''. The most intense storms typically occur in late spring and summer, when stream flows are decreasing and are more typically at mid-flow levels. Most stormwater BMPs are designed to treat small and moderate storms.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#'''Stormwater BMP effectiveness decreases at times when stream flows are decreasing'''. The most intense storms typically occur in late spring and summer, when stream flows are decreasing and are more typically at mid-flow levels. Most stormwater BMPs are designed to treat small and moderate storms.</div></td></tr>
</table>
Mtrojan