Kansas Geological Survey, Public Information Circular (PIC) 9
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Safe Yield and Sustainable Development of Water Resources in Kansas

Marios Sophocleous and Robert S. Sawin

Introduction

The importance of water to every Kansan cannot be overstated. Drinking supplies for urban and rural households, irrigation for crops, and water for livestock, wildlife, recreational, and industrial purposes are uses that touch us all. Water is considered a renewable resource, but on a local or regional level, and in terms of a human lifetime, this is not always apparent. Most of us know of a stream, creek, or river that is now dry or carries less water than it did 25 years ago. The Arkansas River, particularly in western and central Kansas, is a classic example. With the boom in irrigation in the 1960's and 1970's, ground-water levels dropped substantially, again most dramatically in western Kansas (the Ogallala aquifer is an example). In some parts of Kansas, water resources are not being renewed, at least in the short term. Instead, exploitation continues, and aquifers are being depleted and streams are drying up.

State and local agencies have recognized the significance of these problems for some time and have implemented policies that address development of surface and ground water in the state. Termed safe yield, these policies attempt to address sustainable development of water resources--the idea of limiting the use of water now so that future generations will have the same opportunities.

This circular will explain why the entire water system (hydrologic cycle) needs to be considered in managing water resources, and how ground water and surface water interact. It will show why safe yield is not sustainable yield, describe the concept of sustainable development of water resources, and illustrate how that concept can be applied to water-resource management in Kansas.

Bold terms are defined in the glossary.

Determining the water balance for a river basin or watershed serving individual towns or cities with water is in some ways like checking the financial balance of a household--it helps us to see where the expenditures are going and whether we can afford to spend more or whether to restrict expenditures. So, consideration of the water balance enables us to see whether more use can be made of the basin's water resources.

See additional information and illustration of the Water Budget of Kansas.

The Hydrologic Cycle

To understand sustainable development of water resources, it is necessary to understand the relationships between surface water, ground water, climate, landscape, and the biosphere (hydrology). Water on earth circulates endlessly in what is known as the hydrologic cycle (fig. 1).

Figure 1--The hydrologic cycle. Precipitation falls to earth's surface, runs off or infiltrates the ground, then moves back into the atmosphere through transpiration and evaporation.

This cycle has no beginning nor end, but from a global perspective, the oceans are the major source of water. Evaporation from the oceans and, to a lesser extent, the land surfaces supplies the atmosphere with water that condenses to form clouds and falls as precipitation. Most precipitation returns to the atmosphere as evaporation and as transpiration from plants. Transpiration in plants is similar to respiration (breathing) in animals and releases water vapor to the atmosphere. The processes of evaporation and transpiration are usually lumped together and called evapotranspiration. Precipitation that falls on the land either infiltrates the ground to replenish soil moisture or become ground water, or runs off as surface water to form lakes, streams, and rivers. Streams and rivers eventually flow into the oceans, where the cycle starts all over again. This cycle repeats itself over and over again with no loss or gain of water from the global system. On a local or regional level, however, fluctuations of the hydrologic cycle can be dramatic, sometimes producing floods and droughts.

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Glossary || Water Budget of Kansas

Kansas Geological Survey, Public Outreach
Web version February 1998
http://www.kgs.ku.edu/Publications/pic9/pic9_1.html