David G. Litwin, Ph.D.
David G. Litwin, Ph.D.
Postdoctoral Researcher
Hydrology | Geomorphology | Critical Zone Science

About Me

I am a postdoctoral fellow at GFZ Potsdam, the German Research Center for Geosciences, in the Earth Surface Process Modelling section. I completed my Ph.D. at Johns Hopkins University in Baltimore, Maryland in 2023. I am interested in the movement of water through watersheds and the effects that this can have on the long-term evolution of landscapes and ecosystems. Understanding landscape history can help better model and manage water and ecosystems today and in an uncertain future. I build and use computational tools, and collect and analyze field data toward this aim.

Current Research

Groundwater and landscape evolution

My work at GFZ will be centered on the role of groundwater in processes that shape landscapes over long timescales. Project is TBD!

Doctoral Research

Understanding the coevolution of topography and runoff generation

Topography affects how water is stored and released from watersheds, while over long timescales, flowing water shapes topography through erosion and incision of channel networks. Typical landscape evolution models do not have adequate representations of hydrology to capture these feedbacks. In particular, they don’t capture the importance of shallow subsurface flow for runoff generation. In my first PhD paper I coupled hydrological and landscape evolution models and found we showed that hillslope length scales nonlinearly with subsurface transmissivity (permeability times thickness) under the influence of steady recharge (PDF here).

The emergence of variable source area hydrology

In my second paper I took this model further, focusing on how the hydrological function of landscapes coevolves with dynamic climate, soil moisture, and groundwater. I’m particularly interested in the emergence of variable source area runoff generation. In other words, I’m interested in knowing why some places evolve to have saturated areas that expand and contract in response to storms, while others don’t. We found that coevolution produces a strong relationship between variably saturated area and relief, and where a landscape sits on that relationship is conditioned by subsurface permeability and thickness relative to climate. Preprint is available here.

Coevolved topography and runoff generation: a paired watershed study

How does the subsurface affect coevolved topography and runoff generation? This is a central question in critical zone science, and has implications for how different landscapes will respond to climate change and water stress. Our model makes predictions that subsurface transmissivity is a primary control on topography and runoff generation. I’m making hydrometric measurements, conducting saturation surveys, and analyzing topography of two small watersheds with contrasting lithology to test model predictions. Paper is in prep.

Past Research

Drainage divide dynamics when point sinks set baselevel

Steady-state drainage divides fall along the edges of Voronoi polygons separating point sinks, illuminating more general behavior of a simple landscape evolution model. See our poster here.

Understanding controls on the form of flow duration curves

Mean fluxes, including baseflow, quickflow, and streamflow, alone explain quantiles in the flow duration curve across many environmental settings, suggesting emergent behavior of watersheds. See our poster here.

Using electrical resistivity tomography to recover soil properties in a lysimeter

Soil properties at the Landscape Evolution Observatory in Arizona vary in space and may change with time. Theoretical modeling revealed the impact of measurement noise on our ability to determine soil porosity from ERT surveys. See our poster here.


Publications can be found on Google Scholar, ResearchGate, or ORCID.

Computational tools

I’ve built tools for my work that I hope can also benefit the Earth science community. All are open-source, most are well-documented and have extensive unit tests.

Curriculum Vitae

My C.V. is here.

Science Communication and Service

  • Water Underground
    I am a co-editor of the Water Underground blog hosted by the American Geophysical Union and the European Geosciences Union.
  • Geobites
    I write accessible summaries of peer-reviewed hydrology and geomorphology articles for science-curious audiences.
  • American Geophysical Union Hydrology Section Student Subcommittee (H3S)
    I served on H3S for the two year term 2020-2021, helping to establish their website and blog. Posts on the blog feature early career hydrologists and provide support and community resources.


I like roadside geology, hiking, reading fiction, playing the double bass, and sewing my own clothes.