Customer Reviews

Water, Rivers and Creeks

5 star:		(1)
4 star:		(1)
3 star:		(0)
2 star:		(0)
1 star:		(0)

 

 

Water, Rivers and Creeks by Luna Leopold. I still have my copy of Water - A Primer, Dr. Leopold's first update of his slim hydrology primer ($2.95 in 1974). Like Marie Morisawa's book on streams, "Water" has been loaned out many a time, and thankfully it has always made its way back home (if the person who has 'Streams' would please return it...). I wasn't 5 pages into "Water, Rivers and Creeks before I began deciding who should get to borrow the new one first. I was reassured to find that the clear explanations of hydrologic processes remain and that the updating of the text has not diluted its value as an excellent review of hydrology. The order of the topics has been revised to smooth transitions and as a result the book is even more readable than the original. Particularly significant is the fact that the author has thoroughly revised graphics and text to use international units, and broadened the discussion of water policy, especially regarding the impacts of irrigation and dam construction. Part I (Hydrology and Morphology) contains chapters on precipitation, infiltration, groundwater, surface water, channel formation and maintenance, and vegetation. Part II (The Water Resource and its Management) contains chapters on water supply, water use, water availability and quality, land management, water treament and sewage disposal. This useful volume appeals to me as a supplemental textbook university courses, for staff training, and as a reference volume for water policy makers - and even at today's price of $30.00 it represents a great value. - Dr. Jeanette H. Leete, General Secretary American Institute of Hydrology

The author, Luna Leopold, was an authority on water resources, especially fluvial geomorphology. In this book, he provides an introduction to this field at a level suitable for geographers, planners, and policy makers, although engineers and others with more technical background should also find the book useful.

Although the book is a bit rambling and repetitive, the writing overall is still clear and concise, resulting in a book which is generally fairly easy and enjoyable to read. If you don't have time to read it, my summary of the key points is provided below.


Water Supply, Use, and Treatment:

(1) The oceans contain 97% of the world's water, and most of the rest is in frozen icecaps and glaciers. The majority of water flowing into oceans comes from a few very large rivers.

(2) Water supply among and within countries varies enormously, ranging from scarcity to abundance. This is likely to have substantial political and social ramifications in the future.

(3) The days of major reservoir construction are essentially over in the US.

(4) Agriculture accounts for as much as 85% of water use in the US, and about 70% globally. Water in the US is heavily government subsidized.

(5) Water distribution pipes are typically sized to meet peak demands. They're usually 4"to 6" diameter in roadways, and about 1" leading to individual houses. Water pressure in houses is about 60 to 70 psi, which equals about 150 feet of head.

(6) In water treatment, screens remove large materials; grit is allowed to settle out; odor, taste, and appearance are typically improved by settling (eg, using alum for flocculation), filtering (eg, sand), and aeration and/or bacteria to oxidize organic material; followed by chlorination or other disinfection to kill bacteria.

(7) Most pure natural waters, including rain and snow, have a pH of 5.2 to 5.4, with pH of less than 5.0 being considered significantly acidic.


Watershed Hydrology and Groundwater:

(1) The area of a watershed contributing to peak runoff depends on the storm duration, since it takes time for water to flow through the watershed.

(2) About one third of rainfall becomes stream runoff, with the remainder returning to the atmosphere via transpiration (extracted from groundwater by plants) and evaporation.

(3) The rate of infiltration of water into the ground depends mainly on the type of soil and the soil vegetative cover (more vegetation results in higher infiltration), along with how wet the soil is prior to the rainfall. The infiltration rate varies from about ½" to 2" per hour. Infiltration is usually greater than runoff. Infiltrating water doesn't necessarily reach the groundwater table.

(4) The water table surface generally undulates to partially follow the ground surface, rather than being flat.

(5) Water can move through rocks via both cracks and pores.

(6) Substantial water flow in streams long after storms is generally due to groundwater.

(7) Many miles can separate where water enters and leaves the ground, and the water can take months or years to travel this distance. One implication is that it can take a long time to replenish groundwater supplies depleted by overpumping.


Fluvial Hydraulics and Geomorphology:

(1) Runoff hydrographs plot discharge versus time, and the rising limb is typically steeper than the receding limb.

(2) In addition to reservoirs, storage in streams is typically large, which means that flood routing analysis is appropriate and flood peaks are always attenuated.

(3) The flood peaks of tributaries often don't coincide, which results in attenuation of the flood peak for the main channel.

(4) Major floods in large rivers tend not be greatly affected by land cover, and are instead mainly a result of major storms and possibly widespread snowmelt.

(5) The discharge attenuation provided by a reservoir diminishes fairly quickly downstream of the reservoir.

(6) Stream flow velocity is generally highest at the surface and lowest at the bed, with the average velocity being located about 60% above the bed. Since velocity also varies across the width of the stream, total discharge is usually calculated by adding 20 to 30 transverse sections.

(7) Gaging stations typically only measure water surface elevation (stage), which is then converted into discharge using a stage-discharge rating curve (often somewhat linear when plotted on a log-log scale).

(8) Flow velocities in streams generally increase with flow depth and in the downstream direction. Base flow velocities are on the order of 1 to 5 fps, and flood velocities are on the order of 5 to 10 fps, with a max of about 20 fps.

(9) Stream gradients generally go from steeper to flatter when moving downstream. Most streams have pool/riffle sequences, or step/pool sequences in the case of steep streams.

(10) The form of a stream is mainly determined by the sediment carried and the spectrum of flows, especially modest but fairly frequent flows. Larger sediments move as bedload and smaller ones as suspended load, with most of the load usually being suspended load. Bedload usually starts to move at flows just under bankfull discharge. Loss of sediment supply from upstream sources tends to result in channel incision.

(11) The relationship between discharge and recurrence interval often roughly follows a power law. Bankfull discharge usually has a recurrence interval of about 1 to 2 years.

(12) The sinuosity of streams is related to energy conservation. Concave stream banks erode while convex ones experience deposition (associated with point bars), thus maintaining channel width (roughly proportional to square root of average discharge). Resulting back and forth lateral migration forms the floodplain (thus typically comprised of alluvium), although incised streams tend to lack a floodplain. Flow depth and velocity are usually greater at the concave bank. Point bars are usually spaced longitudinally at a distance of about 5 to 7 channel widths. Islands tend to be stable in sinuous streams, but not braided streams.

(13) Stream networks tend to have organized branching patterns which are similar to those found in trees, blood vessels, etc.

(14) Terraces are abandoned floodplains, and typically result from stream downcutting.

(15) Most streams interact with an adjacent riparian zone of vegetation, which promotes bank stability and temperature regulation.