IFS in East Maui – Part I: Nahiku to Huelo Streams
Scott Werden @ Wiki Wai
Mahi Pono, through their subsidiary EMI, gets the bulk of their irrigation water from East Maui streams. The permit they get from the Land Board states how much water they can take. But the courts have also imposed a cap on the diversion of stream water regardless of what the Land Board awards. These rules all affect the total amount of water but there is one additional rule that affects each individual stream, and that is the Instream Flow Standard (IFS). This blog post will explain what IFS is and the problems that exist with its implementation in East Maui.
This blog post topic is divided into three parts:
- Part I (this post) covers two rulings made by the Water Commission on IFS for East Maui Streams,
- Part II goes into the details of how an IFS is determined,
- Part III examines the difference between base flow and storm flow
2018 Ruling on Nahiku, Ke’anae and Honomanu Streams
The left side image is taken from the top of the diversion on the Makapipi Stream, looking up the stream. The right side image is from the same location but looking downstream from the diversion. The stream is obviously dry below the diversion.
The first round of amending IIFS for East Maui Streams became official with the release of 2018 Decision & Order from the Water Commission (CWRM). In that decision, the Water Commission chose to first classify each stream by its potential beneficial uses. Those are summarized here:
- Connectivity. The instream use is primarily driven by habitat connectivity, that is, to allow migration of wildlife up and down the stream. This use can be satisfied with the lowest amount of instream water flow below a diversion.
- Habitat or H90. This use also primarily benefits habitat and wildlife but provides for greater downstream water flow. In this case “H90” means the goal is 90% survival rate for habitat.
- Traditional and Customary Use. The use here is appurtenant, that is, people who live on land that has stream water that was, and is, used for agriculture like kalo. This use can only be fulfilled by opening up the stream so there is no diversion and all water stays in the stream bed.
There is one category missing here: Off-stream use. The Water Commission’s approach to setting IFS is to enumerate the instream uses as required by law and then to basically allow all water that remains to be eligible for off-stream uses. What are those off-stream uses? Currently, for East Maui water, those are primarily agriculture, DHHL (Department of Hawai’i Homelands), and MDWS (Maui Department of Water Supply).
This approach by the Water Commission is not ideal for several reasons:
- All instream uses must be accounted for and if a use is not considered, that use is going to suffer. For instance, streams are not completely independent of groundwater and de-watering a stream will also affect the aquifer. Is that properly accounted for in the current management method?
- The East Maui water cycle is complex both on short- and long-time scales. Streams can be low flowing for weeks and then a big storm will turn them into a flood. Diverting water changes that flow pattern, and this is particularly bad in the method of diversion often used, which is to divert the base flow and leave the sporadic, storm floods in the streams.
- While off-stream irrigation is a beneficial use, it is not necessarily of higher priority than an in-stream use, yet the Water Commission awards the most sought-after component of stream flow, base flow, to off-stream users.
2022 Ruling on Huelo Streams
Diversion on the Ho’olawali’ili’i Stream at the Lowrie Ditch. The stream is coming in from the top-center. The ditch is the channel on the right.
In 2021 the Sierra Club filed a petition to amend the IIFS for 12 additional streams, all located in the Huelo lease area. In 2022 the Water Commission staff released a recommendation for amended IFS for 17 streams (they included branches and alternate names of the original 12).
The recommendation is very different from the 2018 D&O.
- The Water Commission added new management goals, in particular, Recreational Use and Riparian Use. The latter is for people who live on the stream and rely upon it for domestic and/or agricultural activities. The 2018 ruling considered traditional and cultural use which largely meant kalo agriculture, but in 2022 that is replaced with the broader category of Riparian Use.
- The Water Commission in 2022 has replaced an in-stream flow value with an order of what certain diversions must pass onward in the stream. Sometimes this is a percent, sometimes a range of flow. It is not always clear how these newer specs will relate to conditions in the stream so we anticipate some “tuning” of these specs in the future.
- Some of the 2022 recommendations include specific changes to the EMI diversions themselves. But it is not clear how they determined some of the changes ordered as they provide no calculations or engineering diagrams.
Summary
The complete text of the 2018 ruling covering streams in Nahiku, Ke’anae, and Honomanu, see CCHMA1301-20180620-CWRM-Fact-Law-Final.
For the CWRM staff recommendation for Huelo stream IFS, see sb20221115B5-CWRM Submittal B5 to restore Huelo streams.
The following table is a summary of CWRM orders for all affected streams in East Maui. Further details can be found on the Stream Portal of the wikiwai.org website.
| Stream | Lease Area | CWRM Management Goal | CWRM IFS Order (cfs) | Median Flow @1200′ (cfs) |
| Makapipi | Nahiku | Full | ||
| Hanawi | Nahiku | Connectivity | 0.92 | 6.2 |
| Kapaula | Nahiku | Connectivity | 0.56 | 4.3 |
| Wai’a’aka | Ke’anae | None | 0.77 | 0.86 |
| Pa’akea | Ke’anae | Connectivity | 0.18 | 1.5 |
| Waiohue | Ke’anae | Full | 5.2 | |
| Pua’aka’a | Ke’anae | Connectivity | 0.2 | 0.97 |
| Kopiliula | Ke’anae | H90 | 3.2 | 6.6 |
| E. Wailuaiki | Ke’anae | H90 | 3.7 | 7.7 |
| W. Wailuaiki | Ke’anae | Full | 8.9 | |
| Wailuanui | Ke’anae | Full | 3.8 | |
| Ohi’a, Waianu | Ke’anae | None | ||
| Waiokamilo | Ke’anae | Full | 6.1 | |
| Palauhulu | Ke’anae | Full | 5.4 | |
| Pi’ina’au | Ke’anae | Full | 0.38 | |
| Nua’ailua | Honomanu | Connectivity | 2.2 | 0.46 |
| Honomanu | Honomanu | H90 | 4.2 | 3.8 |
| Punalau, Kolea | Honomanu | H90 | 4.9 | 6 |
| Ha’ipua’ena | Honomanu | Connectivity | 1.36 | 4.8 |
| Puohokamoa | Huelo | Connectivity | 1.1 | 8.7 |
| Wahinape’e | Huelo | None | 0.9 | |
| Waikamoi | Huelo | H90 | 3.8 | 6.6 |
| Hanehoi | Huelo | Full | 2 | |
| Huelo, Puolua | Huelo | Full | ||
| Kolea East | Huelo | Specific species habitat | 0.08 | 0.3 |
| Kolea West | Huelo | 0.65 | ||
| Punalu’u | Huelo | |||
| Ka’aeia | Huelo | Aquatic habitat | Flows < 1,8 | 1.3 |
| O’opuola | Huelo | Aquatic habitat | Flows < 1,8 | 1 |
| Puehu | Huelo | |||
| Na’ili’ilihaele | Huelo | Recreational uses | Flows < 5.5 | 13 |
| Kailua | Huelo | Recreational uses and aquatic habitat | 20% of flow | 7.8 |
| Hanawana | Huelo | Riparian uses | Some unknown percentage of the flow | 0.5 |
| Hoalua | Huelo | 1.3 | ||
| Waipi’o | Huelo | Riparian uses | Full flow below New Hamakua ditch | 0.73 |
| Ho’olawa nui | Huelo | Recreational uses | Flows < 1.2 @ Lowrie, 20% flow below New Hamakua | 3 |
| Ho’olawali’ili’i | Huelo | Recreational uses | Flows < 0.7 @ Lowrie, 20% flow below New Hamakua | 3.3 |
| Honopou | Huelo | Full | 2 |