**7. Conclusions**

Quantitative probability-based assessments of water availability are essential for e ffective water allocation and management. Modeling of institutional mechanisms as well as river system hydrology and operation of dams/reservoirs and other constructed facilities are necessary in assessments of water availability. Successful implementation of the TexasWAM System required collaborative e fforts of a large and diverse water managemen<sup>t</sup> community. The shared use of the modeling system has significantly contributed to integrating water allocation, planning at statewide, regional, project feasibility, and operational levels, research and development, and other water managemen<sup>t</sup> endeavors.

Assessments of water availability and supply reliability are performed with the WRAP/WAM system in three stages: (1) compilation and continuing updating of simulation input datasets, (2) performing simulations, and (3) organizing and analyzing relevant frequency and reliability metrics and other information from the simulation results. Water availability assessment applications usually involve revising simulation input datasets to reflect changes in water use requirements or di fferent proposed projects or managemen<sup>t</sup> strategies of interest. The simulation model combines extremely variability natural river system hydrology, complex operations of constructed infrastructure, and water allocation systems that grow in importance with increasing demands on limited resources.

The generalized Water Rights Analysis Package (WRAP) modeling system is applicable in any place in the world and reflects flexibility and practicality necessitated by its evolution within the Texas water managemen<sup>t</sup> community. Lessons learned from the Texas experience in creating and employing a water availability modeling system are relevant worldwide.

**Funding:** This research received no external funding.

**Acknowledgments:** Many agencies and professionals in the Texas water managemen<sup>t</sup> community have contributed to the evolution of the WRAP/WAM modeling system over the past 30 years. However, the information and conclusions presented in the paper are the responsibility of the author without implication of o fficial endorsement by any of these agencies or individuals.

**Conflicts of Interest:** The author declares no conflict of interest.
