10: The Water System
- Page ID
- 175820
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)From Ancient Aqueducts to Modern Water Scarcity
During the fifteenth century, the Mexica (Aztecs) constructed the Chapultepec Aqueduct to bring freshwater from springs at Chapultepec to their capital city of Tenochtitlan, located where the historic center of Mexico City stands today. Early sections of the aqueduct were damaged by flooding in the mid-1400s and were later rebuilt and expanded using more durable materials. During the Spanish conquest of Tenochtitlan in 1521, the system was damaged, but a new aqueduct was constructed during the colonial period along much of the original route. Today, the remains of the Chapultepec Aqueduct serve as a reminder of the long history of engineering solutions developed to provide water for growing cities.
The Chapultepec Aqueduct illustrates a challenge that societies have faced for centuries: securing reliable freshwater supplies for growing populations. As cities expand, local water sources often become insufficient, requiring increasingly complex infrastructure to transport water from distant locations.
This challenge remains highly relevant in Southern California today. More than 20 million people depend on water imported through large aqueduct systems that transport water from the Colorado River, the Sacramento-San Joaquin Delta, and the Eastern Sierra Nevada. Prolonged droughts, climate change, overuse of river systems, declining groundwater supplies, and growing demand have placed increasing pressure on these water sources.
Just as the residents of Tenochtitlan relied on engineered systems to supply freshwater to their city, modern Southern Californians depend on extensive water infrastructure to support homes, agriculture, industry, and ecosystems. Understanding where water comes from, how it moves through the water cycle, and how human activities affect freshwater availability is essential for addressing one of Southern California's most important environmental challenges: ensuring a sustainable water supply for future generations.
Figure \(\PageIndex{a}\): Remains of the Chapultepec Aqueduct in Mexico City. The aqueduct was originally constructed by the Aztecs to transport freshwater to Tenochtitlan and illustrates the long history of engineering solutions to urban water supply challenges.
Image by Diana du Vent CC-BY-SA.
- 10.1: The Hydrologic Cycle and Freshwater Distribution
- How does water move through Earth's systems, and why is freshwater scarce in some regions but abundant in others? This section examines the hydrologic cycle, where freshwater is stored, how watersheds connect ecosystems and communities, and why understanding groundwater, precipitation, and water distribution is essential for sustainable water management.
- 10.2: Water Usage
- This page highlights the importance of freshwater supply for ecosystems and the rising global water consumption, which is at 3,999 km³ annually. It discusses the challenges of water scarcity affecting irrigation and public use, the high water needs for food production and energy, including those for AI data centers, and notes that the U.S.
- 10.3: Water Scarcity and Sustainable Water Management
- Freshwater connects ecosystems, agriculture, and human communities, yet many water sources are under increasing stress from overuse, population growth, and climate change. This section examines the causes of water scarcity and explores sustainable solutions, from conservation and groundwater recharge to desalination and advanced water recycling.
- 10.4: Case Study - The Salton Sea
- The Salton Sea illustrates how water management decisions can transform ecosystems and human communities. This case study examines how agricultural water use, declining inflows, and increasing salinity have reshaped California's largest lake, creating challenges for wildlife, air quality, public health, and long-term sustainability.
- 10.5: Water Pollution
- This page highlights the human-induced causes of water pollution, primarily from agriculture, industry, and sewage systems. It distinguishes between point and nonpoint source pollution and outlines the health risks posed by pollutants like heavy metals and nutrients, which can lead to eutrophication and hypoxia. Historical contamination cases stress the need for regulatory frameworks.
- 10.6: Water Treatment- Protecting Drinking Water and Treating Wastewater
- Safe water depends on two complementary systems: drinking-water treatment, which removes contaminants before water reaches consumers, and wastewater treatment, which removes pollutants before water is returned to the environment or reused. This section explores how treatment technologies protect public health, reduce water pollution, recover valuable resources, and increasingly support water recycling and circular water-management strategies such as Pure Water San Diego.
- 10.7: Preventing Water Pollution and Restoring Watersheds
- This page outlines strategies for addressing water pollution, including regulation, bioremediation, and watershed management. The Clean Water Act has improved U.S. water quality since 1972. Bioremediation cleans contaminants using organisms, while watershed management preserves natural areas to enhance water quality. It also highlights urban landscaping techniques like rain gardens and permeable pavement to manage runoff and improve water quality.
Attribution
This page was heavily revised and rewritten by Erin Rempala and contains adapted content from content originally authored by Melissa Ha and Rachel Schleiger and is licensed CC BY-NC-SA 4.0.