Environmental justice and equity should include access to clean water for all. It is expensive to drill borehole wells, typically over $10,000 US dollars, and so organizations working to provide wells in developing countries have typically installed community wells at some common gathering place. This requires that many users must walk long distances to access these water sources. This limits the quantity of water available to a family, and also creates vulnerabilities for the family member, usually a woman or child, sent for the water since the journey is often made early in the morning or at night in the dark. I have been drilling wells with a Kenyan team since 2010 using a simple, manual percussion hydraulic method developed by WaterForAllinternational.org whereby we can install a well generally for less than $200 US dollars excluding labor. Through their own participation in the drilling process, this low-cost enables families to pay for and drill their own well. In this way, they gain access to a much larger supply of water at or close to home, and eliminate the need and vulnerability associated with walking long distances to procure water for their family. Both the drilling apparatus and the cased well, including the pump, is constructed from materials available off-the-shelf at local hardware stores. Over the years I have made several modifications to the pump design, other infrastructure, and manufacturing process to improve the longevity, simplicity, and interchangeability of the final product. The drilling method is primarily applicable to aquifers lying above bedrock and it is feasible to drill wells to a depth of several hundred feet. The greatest challenge in the endeavor is earning the trust and cultivating the participation of the local community. This presentation will address the drilling process, the well infrastructure, and some socio-cultural aspects of the project.

Wet-surface evaporation equations related to the Penman equation can be represented graphically on vapor pressure () versus temperature () graphs (Qualls & Crago, 2020). Here, actual regional evaporation is represented graphically on (, ) graphs using the Complementary Relationship (CR) between actual and apparent potential evaporation. The CR proposed by the authors can be represented in a simple and intuitive geometric form, in which lines representing the regional latent heat flux, , and the wet surface (Priestley & Taylor, 1972) evaporation rate, , intersect at =0. This approach allows a graphical estimate of (or the corresponding mathematical formulation) without the need to know either the wet surface or the apparent potential evaporation rates. The wet surface temperature is needed, and a calculation method for it is provided. The formulation works well using monthly data from seven sites in Australia, even when the same value of the Priestley & Taylor parameter α is used for all sites.

The polynomial form of the nondimensional complementary relationship (CR) follows from an isenthalpic process of evaporation under a constant surface available energy and unchanging wind. The exact polynomial expression results from rationally derived first and second-order boundary conditions (BC). By keeping the BCs, the polynomial can be extended into a two-parameter (a and b) power function for added flexibility. When a = b = 2 it reverts to the polynomial version. With the help of Australian FLUXNET data it is demonstrated that the power-function formulation excels among CR-based two-parameter models considered, even when a = 2 is prescribed to reduce the number of parameters to calibrate to two. The same power-function approach (a = 2) is then employed with a combination of different gridded monthly potential evaporation terms across Australia, while calibrating b against the multiyear simplified water-balance evaporation rate on a cell-by-cell basis. The resulting bi-modal histogram of the b values peaks first near b = 2 and then at b → 1 (secondary modus), confirming earlier findings that occasionally a linear version (i.e., b = 1) of the CR yields the best estimates. It is further demonstrated that the linear form emerges when regional-scale transport of moist air is negligible toward the study area during its drying, while the more typical nonlinear CR version prevails otherwise. A thermodynamic-based explanation is yet to be found as to why the flexible power function curves (i.e., b ≠ 2) converge to the polynomial one (b = 2) in such cases.