Q&A With Assistant Professor Bwalya Malama

Assistant Professor Bwalya Malama works in the Natural Resources Management and Environmental Sciences Department at Cal Poly.

He does research on hydrogeology, geostatistics and hydrology. Prior to joining Cal Poly in 2014, Malama was a senior member of the technical staff at Sandia National Laboratories in New Mexico, where he investigated groundwater flow and contaminant transport related to geologic disposal of nuclear waste.

Q: Your focus is on understanding sustainable groundwater use in the face of external pressures such as agricultural pumping. What are some of the research methods you use?

A: We primarily install wells and instrument them with water-level sensors to monitor longterm behavior of groundwater reservoirs. To install wells, we use a direct-push power probe capable of reaching depths of 40 feet. The probe also allows us to collect core samples of the subsurface sediment, which we use to map subsurface strata as well as to perform laboratory permeability measurements.

Q: How do natural pressures such as rising sea levels and drought impact groundwater sustainability?

A: Drought has a two-fold effect: on the one hand, it reduces surface water reserves, increasing demand for groundwater, and on the other, it reduces groundwater recharge. The net effect is chronic drops in water levels and depletion of groundwater in storage. Sea-level rise is poised to exacerbate the problem of seawater intrusion, which could render some coastal groundwater reservoirs unusable.

Q: How do you quantify long-term system responses to drought-induced stress?

A: We monitor groundwater levels and groundwater in storage over the long-term. Precipitous chronic drops in groundwater levels with incomplete recovery to historical levels during the rainy seasons, from year to year, are indicative of drought-induced stress. Storage losses are quantified from land surface subsidence measurements.

Q: What technological advances are being made that could have a positive impact on improving groundwater measurement?

A: Advances include geophysical methods for detailed mapping of aquifers, well instrumentation with water level and flow-rate sensors, coupled with monitoring through wireless networks, which allow for real-time monitoring of the state of aquifers by groundwater managers and research scientists.

Q: How critical is it to fully understand groundwater use?

A: In California groundwater accounts for about one-third of the water used in an average year. Groundwater is a limited resource, which if used unsustainably, is subject to undesirable consequences such as failed wells, deteriorated water, and long-term environmental damage. These potential consequences of overuse have been well articulated and enumerated in the Sustainable Groundwater Management Act (SGMA) of 2014.

Q: How do students assist in your research?

A: The projects provide a lot of hands-on learning opportunities. Students are directly engaged in direct-push soil and sediment sampling, well installation and instrumentation, laboratory and field-testing, and some modeling. The wells installed in the agriculture fields at Cal Poly, Chorro Creek Ranch in San Luis Obispo, and Swanton Pacific Ranch in Santa Cruz County were all installed and instrumented with graduate and undergraduate student help.

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