Stephanie Shepherd

Certificate Student 19-20



Capstone Project

A Big Dam Problem

By Lauren Herwehe, Stephanie Shepherd

We should give a dam

Since the early 20th Century the majority of major rivers around the globe have been impounded or diverted to harness the power of water for energy production, transportation, flood control, water storage, and recreation (2, 3). Although society benefits greatly from dams, they come at an often significant cost to ecosystems.

Dams have dramatic impacts both upstream and downstream. Upstream they slow water flow, trapping sediment, fish, and water, hurting river and wetland habitats. Downstream they can dry out entire landscapes and disrupt annual cycles of flooding that supply sediment and nutrients that are critical to ecosystem health. This kills plants and animals and alters aesthetics of beautiful landscapes (4). Thousands of new dams are proposed globally that will potential impact protected areas such as National Parks, UNESCO World Heritage Sites, and UN Designated Ramsar Wetland Sites adjacent to rivers.

This project is a collaboration with the World Wildlife Foundation (WWF) to identify critical habitats around the world that will be impacted by future dam construction. It builds off of the WWF's published dataset and research on Free Flowing Rivers.

 Getty Images


Asking the right question

The question we aimed to answer in our project was: What is the impact of proposed dams on protected areas globally?

We worked to answer this by making two calculations for every country in the world---the total length of rivers on protected lands affected by proposed dams and the total area of protected lands affected by proposed dams.

Finding the data

Various organizations and researchers have gathered information about global rivers that we have leveraged to answer this. We used three datasets, one for rivers and two for protected areas:

River & Proposed Dam Data: The Free Flowing Rivers (FFR) database contains summary information for all major rivers across the globe. It includes an attribute called Degree of Regulation (DOR) which is an index of storage volume of reservoirs on a river versus the total annual river flow. It is reported as a percent, where 0% is a free flowing river and 100% is a reach where the flow is completely altered by a dam. The dataset includes both a current DOR value and one accounting for proposed dams (DOR_PLA), and subtracting these two values allowed us to find which rivers have proposed dams.

Protected Areas: The World Database of Protected Areas (WDPA) is a global database of terrestrial and marine protected areas developed and curated by the International Union for the Conservation of Nature and the United Nations Environmental Programme. We also included Ramsar Areas which are wetland areas of critical importance identified under the Convention on Wetlands (1971).

For context, in Figure 1 below, see protected areas (including both WDPA and Ramsar) and rivers subsetted by degree of regulation.

map of africa with proposed dams and protected areas

Answering the question with open source GIS

We devised a way to answer our research question with the publicly available datasets above and Python. Our step-by-step approach was as follows:

  1. Combine protected areas datasets - First we created a function that combined the two protected areas datasets: WDPA and Ramsar.
  2. Identify large rivers with proposed dams - Next we took the FFR dataset and subtracted the current DOR from the planned DOR for all rivers to filter for only rivers with planned dams. We also filtered to only look at large rivers (long-term average discharge of 300 cms or greater) to keep processing time manageable.
  3. Identify where rivers and protected areas intersect - Then we performed two 'overlays' with the open source GIS package Geopandas:
    • Overlay rivers on protected areas and return only the rivers that intersect protected areas.
    • Do the reverse of above to return only the protected areas that are intersected by rivers.
  4. Add it all up - Finally we summed the above data by country to get the total river length affected by country and the total protected area impacted by country.

Below in Graphs 1 and 2 you will see these results for Africa.

bar chart of protected areas in kilometers around the world

What the data says

At the moment, due to the size of both the protected areas and free flowing rivers datasets, the code times out when processing Europe and North America. We have analyzed data for Africa, South America, Asia, and Australia and will continue working on results for Europe and North America.

Our initial results show that Africa, Asia, Europe, and South America have a high number of future dams - planned or under construction (Figure 2). Future dams are concentrated in countries with both the economic and water resources as well as fewer existing dams. For example, the United States has already built dams on almost all major rivers. Conversely, Australia has few large rivers suitable for hydropower dam construction. As illustrated in the graphs above, potential impacts from new construction is focused in just a few countries per continent. Here the Democratic Republic of Congo has several orders magnitude greater kilometers of river reaches and square meters of protected lands that will potentially be impacted by new dams.

It is important to note these data are limited to what is included in the protected areas databases. There are likely many critical habitats and landscapes that are potentially impacted that are not currently designated as a protected area by the local or federal governments.

Figure 2: Global Distribution of Planned Hydropower Dams on Large Rivers

world map with planned and under construction dams

Future work

As we move forward with the project we will complete the analysis of Europe and North America. We also will partner with experts at the World Wildlife Fund to use these analyses to investigate the magnitude of potential changes for countries of interest and determine what types of protected areas are most at risk.

For more information about this project, including the full code and data analysis, see the repository on GitHub.


  1. Graf, W.L. 2001. Damage Control: Restoring the Physical Integrity of America’s Rivers in The Annals of the Association of American Geographers, 91(1), p. 1-27.
  2. Nilsson, C., Reidy, C.A., Dynesius, M., Revenga, C.. 2014. Fragmentation and Flow Regulation of the World’s Large River Systems in Science, 308(5720), p. 405-408. DOI: 10.1126/science.1107887
  3. McAllister, D.E., Craig, J.F., Davidson, N., Delany, S., Seddon, M. 2001. Biodiversity Impacts of Large Dams. International Union for Conservation of Nature and Natural Resource and the United Nations Environmental Programme Report.


Lauren Herwehe, Education Program Manager Earth Lab University of Colorado Boulder, CO

Stephanie L. Shepherd, Assistant Professor Dept. of Geosciences Auburn University Auburn, AL