Lesson 1a - Overview of Water Sustainability Issues

• Water budget, hydrology and climate

• Overview of integrated watershed management – Human life: health, flood

control, waste management, recreation

– Economy: hydropower, agriculture, manufacturing, tourism

– Environment: water quality, ecosystems/biodiversity

• Sensor networks: wired vs wireless, stationary vs mobile, embedded vs remote

Changing climate & population

The Hydrologic Cycle

• Precipitation - Water being released from clouds as rain, sleet, snow or hail (condensing water vapor).

• Runoff - Precipitation that flows along the surface (e.g., streams), not infiltrating

• Infiltration – Penetration of precipitation into the soil.

• Evapotranspiration (ET) - Water evaporating from the ground and transpiring from plants (returning to the atmosphere)

• Percolation - Downward movement of water through soil and rock beyond the plant’s roots, to storage in deep soil

• Groundwater recharge – Water arriving at the saturated water-bearing unit or aquifer (soil voids filled)

Key Processes in the Cycle

• The Earth’s topography generally determines where the water will flow and accumulate

• The following terminology is common (but somewhat imprecise) – Catchments (also called sub-

watersheds) are relatively small regions that capture precipitation, and create streams

– Watersheds are larger regions that capture runoff from multiple catchments, forming larger streams

– A collection of watersheds feeding a major river is referred to as a basin.

Watershed or River Basin

Stream “order”

• Leopold (1994) defines stream order as "a measure of the position of a stream in the hierarchy of tributaries."

• Simple illustration (upper figure)

• More difficult to see the order in the topo-map (look closely at the topography, and GIS software often has tools to help)

Water balance

• A water balance (or budget) accounts for the flows and storage changes in a hydrologic system

– where I = inflows (L3/T), Q = outflows, and S is the storage (L3)

• The analysis is often performed at different temporal and spatial scales – Large, yearly water balance for a watershed is used to support

resources management

– Small, daily hill slope water balance in support of research

dt

dSQI

Water balance

• Typically, we add specific flow and storage terms, such as:

• where P = precipitation (mm), R = surface runoff (mm), G = groundwater flow (mm), E = evaporation (mm), T = transpiration (mm), and DS = the change in storage over the specified time period (mm)…notice the units here (see next slide)

• Example: For a 120 hectare lake, with a total volume (storage) of 20,000 m3, an average inflow of 0.42 m3/s, an average outflow of 0.37 m3/s, and total monthly precipitation of 33 mm, estimate the evaporation loss from the lake (see next slide).

STEGRP D

inflow

How do the units work here? Do we have all the necessary information? Can we justify neglecting some of the processes? How might our analysis need to change for longer-term planning purposes?

STEGRP D

Beyond hydrology (amounts and timing of water) to water resources management (sustainability)

• Pristine watershed • Human-dominated watershed

Water quantity and Sensors

• Insufficient water quantity (e.g., drought conditions)

• Excessive water quantity (e.g., flood conditions)

• Changes in the timing of water availability (e.g., climate change causing earlier snow melt)

• Monitor water use more carefully (e.g., precision irrigation, “micro-metering” in the urban environment)

• Monitor precipitation and flows, actuating alarms and emergency responses

• Monitor watersheds more completely (precipitation, snow pack, soil moisture, stream flow)

Problems Solutions

Water quality and Sensors

• Increasing salinity levels in soils

• Decreasing dissolved oxygen (DO) levels in rivers

• Polluted rural groundwater drinking water

• Monitor irrigation water quality, ET, and soil salinity levels over time

• Monitor DO levels and input flows (e.g., from industries) to identify major sources, implement regulations on industrial effluents

• Develop remote treatment systems and monitor remotely to identify maintenance needs (e.g., change RO filter)

Problems Solutions

Ecosystem Services provided by water

• Ecosystem services – The benefits to mankind provided by natural resources and processes

• For water, these might include: – Drinking water supply

– Irrigation water supply

– Dilution and removal of waste; disease prevention

– Hydropower

– Floods (help soils)

– Habitat for fish (for food)

– Habitat for water plants and animals…biodiversity

– etc.

• What is the value of these services?

Quantifying ecosystem value and tradeoffs

• Some services have clear monetary value (e.g., hydropower)

• Others do not have clear monetary value (e.g., biodiversity of a habitat)

• Example: How much water to release to sustain fish habitat vs. How much water to retain for irrigation supply?

Water and Sustainability

• Sustainability questions are coupled to quality of life questions

• Our population is large now, so freshwater is becoming a scarce commodity – Not always available when and where we

need it

• Now and in the future, we need to learn to monitor and forecast the quantity and quality of our water resources

• We need to be able to properly and efficiently address questions difficult water allocation questions

• These questions are most difficult when (a) population is high and (b) climate is semi-arid…in other words, in many places in the world!

The approach to sustainability: Higher resolution observations Sensors deployed at multiple spatial and temporal scale

inflow

Let’s revisit the previous example problem What if inflows and outflows were transient? What if groundwater contributions were unknown but significant? What if the precipitation fell in heterogeneous patterns on and around the lake?

STEGRP D

Too simple. We will need a more detailed watershed model (more coming on this)

Weather station; obs well; flow station

Day 1: Recommended reading and websites:

• Montgomery, J.L. et al., (2007) The WATERS Network: An Integrated Environmental Observatory Network for Water Research, Environmental Science and Technology, 42(19), 6642-6647. – This paper summarizes a U.S. vision for achieving more complete monitoring and forecasting

capabilities for its freshwater resources, including drinking water and ecosystems. [Available on course website]

• Goldman, J. et al., (2007) Distributed Sensing Systems for Water Quality Assessment and Management. White paper commissioned by the U.S. Environmental Protection Agency, published by the Woodrow Wilson International Center for Scholars, Washington DC, 35 pp. – This paper provides an overview of available sensor types and suggests strategies for combining

different sensors to provide useful information about environmental systems. [Available on course website]

• Critical Zone Observatories (CZO) website: http://criticalzone.org/ – The CZOs are examples of the most advanced types of hydrologic observatories. They are

research networks that combine ground- and remote sensing with watershed simulation techniques in an attempt to provide “digital” watersheds.

• National Ecological Observation Network (NEON) website: http://www.neoninc.org/ – This network is under construction and will collect data across the United States on the impacts

of climate change, land use change and invasive species on natural resources and biodiversity (water is part of this, but mainly it concerns ecosystems).

• Center for Coastal Margin Observation & Prediction (CMOP) website: http://www.stccmop.org/ – This is an excellent example of an integrated sensing and modeling effort in the Pacific

Northwest region of the U.S.