**5. Conclusions**

Water governance structures like those in Nebraska indicate that, even in a large-scale, complex common pool resource such as hydrologically connected surface and ground water, a "bottom up" system is feasible. Evidence from the field interviews suggests that local ground water users have accepted the moratorium imposed by the NRD, because it reduces uncertainties about the future, including the possibility of more devastating restrictions if previous patterns of consumptive use had continued unabated as those observed in Figure 3B,C. The exception to these findings, however, is that the GWMPA framework limits participation by surface water providers in the IMP process. This limitation becomes relevant in cases where surface water contributes to the recovery of ground water levels (Figure 3A).

Interviews revealed concern among some stakeholders with this arrangement, because they perceived it as resulting in a less-than-equitable process and outcome in terms of water appropriation. This tension between surface and ground water providers and users stems from the bifurcated system of water laws in Nebraska. Laws governing surface water use according to the doctrine of prior appropriation with its associated principle of seniority evolved independently of doctrines of reasonable use and correlative rights governing access to ground water in the state. An over-appropriated designation requires offsets to depletions of surface water flows from ground water use dating back only to 1997, even though there are older surface water appropriations impacted by those earlier depletions. Conflicts stemming from this bifurcated system, especially in over-appropriated areas, are beyond the scope of the GWMPA and the IMP process [32].

The tension that results from this bifurcated system has complicated the implementation of the IMP process. In fact, the significance of the hydrological connection between surface and ground water wasn't fully appreciated by decision-makers during passage of the GWMPA and the framework splitting jurisdiction between NeDNR and the NRDs [4]. As a result, there is a gap in the alignment of the legal framework with CPR design principles, in particular the principle that individuals who directly interact with the common pool resource and with one another are in the best position to modify operations over time, and that they are therefore motivated to participate in decision-making [2]. As the experiences of some interviewees have suggested, their participation in the development and implementation of the IMP is limited in scope, especially decisions about the extent of controls on ground water use that impact surface water supplies. These limitations, in turn, affect perceptions of an inequitable system for imposing sanctions and resolving conflicts. Ultimately, these limitations could impact the sustainable managemen<sup>t</sup> of hydrologically connected surface and ground water supplies in the UPB.

The effectiveness of integrated managemen<sup>t</sup> strategies may depend on the extent of connectivity and the inherent complexity of the drivers of ground water-level changes. Nonetheless such analysis is beyond the scope of this study it is evident that approaches such as those proposed by [6,7,28] could be predict changes in ground water levels in response to water policies and climate variability, and consequently the CPR design principles.

Ostrom's principles emerged from years of empirical research demonstrating their effectiveness as an alternative to hierarchical governmen<sup>t</sup> or private market allocation of common pool resources. This study used Ostrom's framework to study the implementation of the IMP process in the field, and it identified major areas of alignment suggesting that there is potential for Nebraska's decentralized approach to achieve sustainable levels of surface and ground water. Nevertheless, the future effects of severe droughts and long-term climate change are largely unknown at this time, and more comprehensive reforms may be necessary to involve surface water providers and users in the integrated managemen<sup>t</sup> of hydrologically connected common pool water resources. These efforts should lead to the design and creation of a more climate-resilient water infrastructure based on a better understanding of the socio-ecological functionalities of the surface water and ground water resources.

**Author Contributions:** Conceptualization, F.M.-A. and T.A.-M.; methodology, F.M.-A., T.A.-M. and A.A.; software, F.M.-A., T.A.-M. and A.A.; validation, F.M.-A., T.A.-M. and A.A.; formal analysis, F.M.-A., T.A.-M. and A.A.; investigation, F.M.-A., T.A.-M. and A.A.; resources, F.M.-A., T.A.-M. and A.A.; data curation, F.M.-A., T.A.-M. and A.A.; writing—F.M.-A.; writing—review and editing, F.M.-A. and T.A.-M.; visualization, A.A. and F.M.-A.; supervision, F.M.-A. and T.A.-M.; project administration, F.M.-A. and T.A.-M.; funding acquisition, F.M.-A. and T.A.-M. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors wish to thank the Nebraska Department of Natural Resources for funding this research. Some research ideas and components were also developed within the framework of the USDA National Institute of Food and Agriculture, Hatch project NEB-21-166 Accession No.1009760, the Robert B. Daugherty Water for Food Global Institute at the University of Nebraska and the University of Nebraska-Lincoln Institute of Agriculture and Natural Resources-Agricultural Research Division.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of University of Nebraska-Omaha Institutional Review Board (IRB#745-14-EX).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Restrictions apply to the availability of interview data. As reflected in our Institutional Review Board protocol, the interview data was obtained from individuals on a confidential basis, and further disclosure of this data could directly or indirectly reveal their identities.

**Acknowledgments:** The authors also wish to thank Jesse Bradley and Jennifer Schellpeper from NeDNR for fact-checking the original report.

**Conflicts of Interest:** The authors declare no conflict of interest.
