In this article, I first review some aspects of early western water allocation, particularly the way in which riparianism was initially superceded by prior appropriation and the justification then and now for the no-sharing rule of prior appropriation. Contemporary difficulties of overappropriation are then discussed, as are conventional state responses to overappropriation. I then analyze several examples from California of state equitable apportionment, which I view as an unconventional but important response to overappropriation in western states, and offer equitable interpretations of two well-known federal water law decisions.

I. Introduction

II. Early Western Water Allocation

III. Contemporary Overappropriation ... A. Dormant Rights ... B. Tributary Groundwater ... C. Overdrafting ... D. Separate State Schedules

IV. Conventional State Responses to Overappropriation ... A. Enforcement of Priorities ... B. Augmentation of the Supply

V. Equitable Apportionment Cases in California: An Unconventional State Response to Overappropriation ... A. Pasadena v. Alhambra ... B. California's Delta Water Cases ... C. The Reasonableness Cases

VI. Equity in Federal Cases

VII. Conclusion