Conceptually & emotionally, the Hualapai have often referred to haitat when discussing the question of the Reservation's northern boundary that goes "to" and "along" the Colorado River adjacent to the part of the Grand Canyon National Park boundary that is set "on the south bank" of the Colorado.
Translated, this Hualapai term refers to the "spine" of the river, the middle of the river. As used, it refers to the Hualapai idea that before whitefolk interfered, the river marked the northern limit of their territory, and the southern limit of Southern Paiute territory. In this division, the line was the middle of the river, its spine, haitat. In other terms, from time immemorial, the Hualapai exclusively used and occupied the land from haitat south, the Southern Paiute from that line on north.
In trying to understand usage of this term, I wonder if it is like a bodily spine, or is it just a linear site of zero width? Does it truly refer to a spine for the river, or have a wider implication of a spine for the Hualapai territory? When Hualapai use(d) the term, what image resonated for them?
The term, so far as I know, does not show up in discourse over the boundary as recorded until the Bridge Canyon dam + Indian Claims Commission (iCC) period of 1949 - early 1950's. It might be in the papers making up the Santa Fe RR. case, but the northern boundary itself was not in contention, so it might not. If it was used 1) before 1880 and/or 2) between 1880 and 1949, I would be anxious to find references.
What does seem reasonable to me, given the testimony and evidence of trans-river activity by both Hualapai and Southern Paiute, is that the river, haitat, was not seen as a barrier, a demarcation of tabu and hostility. Instead, the river was the normal limit of Hualapai lives, and now and again someone would cross it in either direction for any one of a number of activities: trade, a partner, escape, etc. This is important, since it implies that the river as a place, rather than just a line, was mutually used, not exclusively.
This brings up the ICC, which took testimony and evidence, and heard argument about the northern boundary. Its 1960's finding that the boundary did not go to the middle of the river, but was on its southern shoreline was contested, then argued and affirmed. (see below for another detail about this decision). That is, the river itself was found not to be in the aboriginal territory of exclusive use and occupancy by the Hualapai. The weight to be given to the ICC is an open question, but it is the only explicit consideration/adjudication given the northern boundary until 1972-5, the GCNP Enlargement Act.
Before the ICC, of course, came the army delineation of a reservation. We can look at the description, "to" and "along" the Colorado River, from two angles: 1) What did Palfrey & Price, the army officers, think and do? 2) How do disputants over the years interpret what they did? I have already covered these points at length; I only want to reinforce here my notion that the officers used the river as a convenient limit, and were not conceiving of a specific legal line with a meaning under prevailing law. Certainly Palfrey's 1882 map does not attempt to be specific about the northern boundary. Of course, the officers might not have known about haitat or perhaps no Hualapai in their discussions brought it up; maybe it came up, and the officers rejected it. In any case, the Order establishing the Reservation does not enshrine haitat as a concept or line for the Reservation.
The point of this long "methinks the lady doth protest too much" argument is that haitat makes sense considered as Hualapai lore, and is repeated often as part of their claim to a northern boundary that includes to the middle of the river. Nevertheless, in the political-legal system we live under, and which served the Hualapai well, if not quickly, in the Santa Fe case, haitat has, over the past 131 years, been ignored or considered irrelevant or rejected in delineating the Reservation boundary.
Which leaves us with the National Park Service claim that GCNP's boundary goes to some high water mark to deal with. Two points here: It would be useful to learn more about how Superintendent Stitt decided to make that claim in 1975, and we need to see what the current consideration of GCNP's boundary settles on and how that decision is justified.
Additional nit on the ICC:
In considering their decisions on boundaries of aboriginal territory and consequent compensation, the ICC had a decision grid:
Was the river to the middle decided to be part of Hualapai aboriginal territory?
If not, then no compensation would be paid, whether it was in the Reservation or not.
If it was aboriginal territory but not in the Reservation, then compensation would be paid.
But if aboriginal and in the Reservation, there would be no compensation since the Hualapai own it.
ICC only decided about it not being aboriginal territory; it did not decide whether river to its middle was in the Reservation. That is, ICC said it did not accept the Hualapai claim of having to its middle from time immemorial for exclusive use. However, ICC did not have any say about the Hualapai claim of having to its middle arising from the Presidential Order granting it to them.