Where did the water you drank today come from? With a roll of the dice, students will learn the complex movement of water through role-playing and will identify the states of water and changes in state as it moves through the water cycle.
Engineers view percipitation as "stormwater." A "storm event" is the quantity (amount and intensity) and its duration (time). But where does this stormwater go within the urban environment, and how does the urban water cycle differ from the natural water cycle? Let's follow the urban water cycle, starting with stormwater, and see where the water travels and why urban infrastructure needs to accommodate stormwater.
Have students use their own trackers to write creative stories about the places water might visit in its movements.
Water is constantly in motion. Sometimes quickly, as in a fast-flowing river, but sometimes it moves quite slowly, like in underground aquifers. Understanding the details of how water moves about, on a watershed scale, is critical to understanding how both dissolved contaminants and those attached to particles that are carried along in a water stream, are transported around the watershed. The movement of water, the water cycle, is often shown as a simple circular cycle in which water evaporates from the ocean, is carried over land, falls as rain, and then is transported back to the ocean through rivers. This depiction tends to oversimplify the actual movement of water. There are many places, or compartments, where water may be found during its cycle, and the actual path any given water molecule follows within the complete water cycle can be quite varied and complex. Nor do such simple figures help to convey the period of time that any given water molecule may spend within certain compartments. For instance, the Antarctic Bottom Water takes over 250 years to travel along the bottom of the Pacific Ocean before it re-surfaces in the Aleutian Islands.
Water may change state from a liquid to a gas or solid as it travels along its path. Water in its liquid form is the most visible and obvious. Water can be seen flowing in rivers and surging in ocean waves. Water even travels underground, though slowly, where it seeps through the spaces between grains of soil, sometimes coming to the surface as artesian springs. Although gravity works on ground water, geologic formations play a critical role in determining which direction water actually travels while underground.
Living organisms also move water about. Water, either directly consumed as liquid or extracted from food, is carried within bodies. It then leaves as a gas during respiration, is excreted, or may evaporate from the skin as perspiration.
Plants are the major biotic movers of water. Their roots collect water for distribution throughout the plant. Some water is used in photosynthesis but most travels to the leaves where it is easily evaporated or transpired. Plants and their roots are also a major determining factor in the ability of a landscape to retain surface runoff.
Although most water vapor cannot be seen, fog and clouds do give some indication of water vapor in the atmosphere. Water condensation, seen as early morning dew or drips on a cold glass, is one visible example of the water vapor present in our air. In clouds, water molecules condense and collect on microscopic dust particles until they reach such a weight that gravity pulls the
water down as precipitation.
The impact of gravity on the water cycle is viewed elsewhere. Liquid water certainly conforms to the laws of gravity as it flows, but even ice on mountaintops obeys the laws of gravity as glaciers slowly move downward.
The following role-playing game allows you to better understand the complexity of the actual water cycle. Stations are set up for each of nine different compartments of the water cycle. Students will represent the water cycle. A roll of the dice at each station tells you where to move next or to stay. This game is meant to be played with a group of people, so that the path each player takes can be compared with everyone else’s. (It can be done over and over by one person to achieve the same results though. Adjust the following instructions accordingly.) Trackers – either colored beads or strips of paper – are used to track each person’s journey through the water cycle.
Stormwater that collects on surfaces becomes stormwater runoff. Stormwater runoff is often guided along parking lots, curbs, and streets to gutters and then into a storm sewer or combined sewer system. A storm sewer is a series of pipes that collects and transports only stormwater. A combined sewer is a series of pipes that collects and transports stormwater and wastewater. Combined sewers are common in several of the oldest U.S. cities such as New York, Boston, and Chicago. However, newer cities such as Tampa, Austin, Asheville, San Diego, Portland, and Seattle do not have combined sewers. Atlanta has a mix of both.
Stormwater runoff that enters a storm sewer system is transported to surface water collection areas. Surface water may include stormwater ponds, rivers, lakes, estuaries, bays, dams, wetlands, canals, levees, oceans, or Gulf Coast areas.
Water is extracted from surface water systems and groundwater sources by drinking water facilities to produce the clean water that comes out of our faucets and shower heads and fills our washing machines, dishwashers, and toilets. But where does this water go when it leaves our homes?
The water that leaves our homes is typically classified as wastewater and enters into a combined sewer system or a sanitary sewer system. A sanitary sewer collects only wastewater and does not include stormwater. Both sanitary and combined sewer systems travel underground in cities as part of the urban infrastructure, transporting our wastewater to a wastewater treatment facility. Here, water is cleaned/treated and released back into the surface water collection systems.
By contrast, the natural water cycle is free of human-made objects and infrastructure, and is mostly composed of pervious surfaces. These previous surfaces promote infiltration, resulting in high levels of groundwater recharge (absorption or replenishment) and groundwater flow when compared to stormwater runoff.
