8 essential questions to ask before installing an irrigation system

OLYMPUS DIGITAL CAMERA
Photo credit: nrcs.usda.gov

Irrigation systems offer a variety of benefits.  They allow for the growth of a wider variety of crops.  They can be timed so that the hands-on portion of crop production is a little less cumbersome.  They protect crops from irregular and dry weather conditions.  They support leaching, which can remove harmful, crop-damaging salts within in the soil.  Crops that are supported by irrigation tend to be much more productive.

To reap said various benefits, several considerations must be made and an assortment of essential questions must be answere

1. Why do you want an irrigation system?

2. What type of soil do you have?

      Do you have sandy, loamy or clay?  It could also be (and often is) a combination of the           three.

ds_07_usda-triangle
Photo credit: salinitymanagement.org

3.  What is the amount and distribution of the precipitation?

  • When does the growing area receive the most rain?   
  • Is the rain equally distributed throughout the year?
  • Are there rainy and dry seasons?
  • How much precipitation does the area receive annually?
    • Arid: less than 200mm/year
    • Semi-Arid: less than 400mm/year
    • Humid: more than 1000mm/year
    • Semi-humid: more than 800mm/year

4.  What are the temperature ranges and averages?

Are there hot and cold seasons?
Are there temperature extremes?

5.  What is the climatic water balance?

How does water flow in and out of your environmental system?
Is there a renewable source of water that can support the irrigation system?  

***If the answer is no, AN IRRIGATION SYSTEM SHOULD NOT BE INSTALLED!!!!

6.  What are the soil conditions?

  • Water storage capacity/Available water capacity (AWC)
    • This is the range of available water that can be stored in soil and be available for
      growing crops

      • formula: (water content at field capacity) – (permanent wilting point)
  • Field capacity (FC)  
    • This is how much soil moisture or water content is retained in the water after the excess water has drained and the rate of downward movement (free drainage) has decreased.  This typically takes place 2 – 3 days following rain or irrigation (assuming the soil is pervious and uniform in structure and texture).
  • Soil depth
  • Humus content
    • Humus is composed of decayed organic matter (plant and animal).  As it decomposes, it provides plants with many nutrients required for their growth.
  • The slope of the growing area
table_03
Photo credit: agry.purdue.edu

7. What crops do you want to grow?

  • What are the water demands of the desired crops?
    • Are the crops perennial (trees, vineyards) or annual (tomatoes, beans)?
    • How do the chosen crops react to water stress and irrigation?
    • Will cover crops be used?
    • How and when will crops be rotated?

8. What water will be used for the irrigation system?

  • Is there renewable water (not old water)?
    ***if not, AN IRRIGATION SYSTEM SHOULD NOT BE INSTALLED
  • What type of water will be used?
    • Recycled, waste or fresh
  • In what condition is the water?
    • Salt levels
    • PH levels
    • Presence of heavy metals
    • Are there hygiene issues (disease, effluence)

Once these questions have been answered, the next step is deciding the type of irrigation system that will be used.  

See also:

agricultural irrigation

the purpose of agricultural irrigation and the advantages and disadvantages of mainstream methods

Irrigation is defined as the artificial application of water to the soil through various systems of tubes, pumps, and sprayers.  Approximately 20% of the world’s agricultural land is irrigated, yet 40% of the world food supply comes from irrigated lands with 70% of the world’s freshwater reserves being used for irrigation purposes.  

The main reasons for irrigation are:

1. Not enough rainfall to support crop growth.  

This may be due to rainy and dry seasons, drought or arid or semi-arid climate conditions.  Irrigation systems may also be used to maintain consistent moisture levels even in areas with moderate precipitation levels as it has been shown to improve crop performance.

and

2. High soil salinity levels.  

High soil salinity levels can be a natural occurrence which is the case in many semi-arid and arid locations or a result of poor agricultural practices and ineffective drainage.  In cases impacted by salt levels in the soil, irrigation must often be coupled with drainage in order to achieve the desired benefits.  

There are two main types of agricultural irrigation – gravity powered and pressure driven systems.  Gravity powered systems are, as the name implies, driven by gravity.  Pressure driven systems require an electrical pump in order to provide the irrigation system with water.

Examples of gravity powered systems include:

  • Furrow irrigation systems, basin irrigation systems and hand irrigation systems.

Advantages of Gravity Powered Irrigation Systems

  • Low-cost – gravity is free and simple irrigation systems can be developed to use this wonder of physics
  • Promotes social interaction – many community members need to work together to ensure the success of irrigation systems, particularly those dependent on water that comes from long distances (ex. mountain runoff)
  • Can be used indefinitely as long as the irrigation system is well-maintained

Disadvantages of Gravity Powered Irrigation Systems

  • Requires constant monitoring to ensure that the crops are not damaged by too much/too little irrigation water
  • Difficult to adapt to the specific needs of plants
irfurrow
Furrow Irrigation
irrigation-9
Basin Irrigation, Photo Credit mit.edu

 

Examples of pressure powered irrigation systems include:

  • Drip irrigation systems, sprinkler irrigation systems and pivot irrigation systems.

Advantages of Pressure Powered Irrigation Systems

  • High water efficiency
  • Very adaptable to the needs of the plants which allows a wider variety of crops to be grown – especially those of higher value

Disadvantages of Pressure Powered Irrigation Systems

  • High use and maintenance costs (parts replacement, electricity costs)
  • Expensive to install
  • Requires a high level of education and training for use (the most advanced system in the world can be installed, but if the people don’t know how to use it, it’s useless.)
  • Needs to be replaced every 10 – 20 years as the technology becomes outdated
drip-irrigation-system-for-trees-2
Drip Irrigation System, Photo Credit: heritageoakfarm.com
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Sprinkler Irrigation System, Photo Credit: ers.usda.gov
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Pivot Irrigation, Photo Credit: ers.usda.gov

 

 

precipitation

There have increasing reports of severe weather conditions throughout the world. Certain areas are facing record-breaking water shortages while others are faced with unprecedented flooding. There are a myriad of circumstances that are leading to these conditions. However, the amount of precipitation an area receives is a dominating factor.

Precipitation is part of the atmosphere and composed of water or water vapor. Atmospheric water exists mostly as vapor, but briefly and locally becomes a liquid (rainfall and cloud water droplets) or a solid (snowfall, cloud ice crystal and hails).  

Precipitation events are recorded by gauges at specific locations. Point precipitation data is used collectively to estimate the areal variability of rain and snow. Rainfall data are usually represented as mm/hr, mm/day, etc.

When precipitation falls, it provides the water necessary for groundwater recharge. This is the process of  surface water percolating through the soil to become groundwater. It is the main way in which water enters aquifers. Aquifers are the main source of potable water for humans.

Rain drops may be considered falling bodies which are subject to gravitational, buoyancy and air resistance effects. Raindrop velocity at equilibrium (also known as terminal velocity) is related to the square of rain drop diameter. Larger drops fall faster and are able to collect more water during the fall. However, if a drop is too large (greater than 6/7mm in diameter), it tends to break into smaller droplets.

090723-drop-burst-02

As with the other components of the hydrological cycle, the sun is the driving force behind precipitation. Precipitation comes from water vapor generated by the solar radiation from land and water. It requires vertical flowing air, as well. As water is composed of hydrogen and oxygen, it is lighter than the air when in its vaporous form.

Precipitation is affected by a variety of factors: wind, temperature, atmospheric pressure and local landscapes. It is created in two ways:

  1. Ice crystal process – aerosols act as the freezing nuclei. Ice crystals grow around the nuclei and fall to the ground, although they often melt before hitting the ground.
  2. Coalescence process – small cloud droplets increase in size as they come in contact with other droplets through collision.

The three major categories of precipitation include:

  1. Convective heating air near the ground expands and absorbs more water moisture. The moisture-laden air moves up and gets condensed due to lower temperatures, thus producing precipitation. Conductive precipitation ranges from light showers to thunderstorms with extremely high intensity.
  2. Orographicthe uplifting air caused by natural barriers such as mountain ranges.
  3. Cyclonic – the uneven heating of the earth’s surface by the sun results in high a low-pressure regions and air masses move from high-pressure regions to low pressure regions. If warm air replaces colder air, the front is called a warm front. If cold air displaces warm air, it is called a cold front.

Precipitation is also one of the factors that aids in the climate classification of a given area. If an area receives less than 200mm/year it is considered arid. If it receives less than 400mm/year, it is considered semi-arid. Conversely, if an area receives more than 1000mm/year it is considered humid and if it receives more than 800mm/year it is classified as semi-humid.

reasons for and benefits of agricultural drainage

Agricultural drainage serves two purposes. The first is for the removal of excess surface and subsurface water.  The second is to remove excess soluble salts with the (excess) water from the drained soil profile. 

drainage
source:  bae.ncsu.edu

There are two options for drainage systems. The first is a surface drainage system. A surface drain removes excess water from the surface of the land.

The second is a subsurface drainage system. A subsurface drainage system is used to control the water table in the soil. They can be open drains, which are open ditches with an exposed water table, or pipe drains which are buried pipes.

water table drainage
source: ohioline.osu.edu

Both types of drainage are employed to direct excess surface water to a collector drain in order to prevent ponding.

ponding
source: purdue.edu

The three main components of drainage systems are as followed:

  1. A field drainage system
    This system is used to control the water table and prevent ponding. This component is the most important part of the drainage system. It is comprised of a network which gathers excess water from the land. This is accomplished with the assistance of field drains. Supplemental measures to direct water to the drains may be taken.
  2. A main drainage system
    This part of the drainage system brings the water away from the farm to the outlet point. The water comes from the field drainage system, surface runoff and groundwater flower using a main drain known as a canalized stream. This means that there was an existing stream that was altered to improve the flow.
  3. An outlet
    This is where the drainage water is led out of the area and discharged into another body of water (lake, river, sea). An outlet will either be gravity powered or require a pumping station.  If it is gravity powered,  the water levels rise and fall.  An outlet will require a pumping station if the water levels in a drainage system are lower than the levels of the receiving body of water.
outlet
source: bae.ncsu.edu

There are several benefits of agricultural drainage.  The biggest and most important being the improvement of aeration within soils which results in better yields. This is due to the fact that:

  1. The crops can root more deeply
  2. The choice of types of crops that can be planted is expanded
  3. There will be fewer weeds
  4. Efficiency in fertilizer use will be improved
  5. Denitrification will be reduced
  6. Grass swards will be better

There are also additional benefits not related to aeration. They include:

  1. Easier access to the land
  2. Greater bearing capacity in the land
  3. The soil has better tilth and workability
  4. Tillage operations can take place over a longer period of time
  5. A better environment for micro-fauna (ex. Earthworms) is created which improves permeability
  6. Crops can be grown earlier due to increases in soil temperature

Drainage also makes it possible to inhibit soil salinity.  Soil salinity levels indicate the amount of salt presence within a soil. If there is too much salt, plant growth will be retarded.  To remove the excess salts from the soil, leaching is encouraged.  Leaching is the process of nutrients or salts being removed from the soil with water.  Leaching can occur naturally or as a result of irrigation and drainage systems. Sometimes leaching is necessary to repair land that has been negatively impacted by agricultural activities. It is also used to protect the root zone from being salinized by the capillary rise of saline water. Such safeguards allow for a wider variety of crops to be grown.

sources:

https://www.bae.ncsu.edu/topic/drainageadvisory/background.php

https://www.researchgate.net/publication/272507858_Drainage_of_Irrigated_Lands

http://www1.frm.utn.edu.ar/laboratorio_hidraulica/Biblioteca_Virtual/Subsurface%20drainage%20practices/Part_1.pdf

soil sealing: what it is and why it’s important

soil sealing2

Soil. A living, breathing fundamental component of the world.  Without it, we would not be able to grow food. There would be no trees and plants growing to provide us with the delicious oxygen so necessary to our existence. Our water would not be purified. We would more or less just be screwed. Yet, we continue to cover this valuable resource with impermeable materials like asphalt and concrete in an effort to build housing, roads, factories and parking lots.

Sure, we need those things too. There is no denying it. But, there are alternatives to impervious materials.They may cost a bit more, but how much exactly is clean water worth? To those without it, it is invaluable or at least much more valuable than a new parking lot. What is the value of a house that has not been destroyed by flooding? Certainly much less than one that is floating down a river towards the ocean in pieces because it was destroyed by flash flooding.

The main perpetrators of this crime against nature are suburban sprawl, a rapidly growing population, and increases in transportation demands. The rapid migration to urban areas is exacerbating this issue.

surface sealing

Some soils are naturally prone to sealing – like those in Southwest USA. However, this is often the result of  poor soil quality (issues with aggregation). There are also issues with soil sealing as a result of poor agricultural practices, such as driving large farm equipment over wet soils and leaving large tracts of land bare of vegetation which would typically improve the structure of the soil and mitigate issues created by rainfall.

Regardless of the source of sealing (although it is usually the fault of humans), the consequences of soil sealing are many including, but certainly not limited to:

  • Increased flood risks
  • Reduced groundwater recharge
  • Increased water pollution (caused by runoff)
  • Loss of biodiversity as a result of habitat fragmentation
  • Disrupted gas, water and energy fluxes

To deal with the issue of soil sealing, many steps can be taken.

The best option is to stop engaging in practices that lead to soil sealing. This means using land more efficiently and intelligently, as well as using existing infrastructure. However, we as humans sometimes have a difficult time changing our habits. This may require that alternatives to impervious concrete and asphalt be more widely used (as alternatives already exist.  see: http://www.perviouspavement.org).

In regards to agricultural causes, crop rotations should be employed, heavy machinery should not be used on wetlands, and cover crops should be planted to encourage aggregate formation and water absorption.

Should we as a species work to address the issue of soil sealing (or even take preventative measures), a myriad of negative consequences could be mitigated. Then maybe one less family will lose everything because of a flood, one less crop will be destroyed taking us one step closer to food security, and mother nature can continue to do her thing – something we can all appreciate (even if we don’t know it).

sources:

http://www.agprofessional.com/news/soil-sealing-crusting-water-erosion-and-poor-soil-health
http://www.concretenetwork.com/pervious/
http://ec.europa.eu/environment/soil/pdf/guidelines/pub/soil_en.pdf

 

an introduction to hydrology and essential terminology

Hydrology is a branch of the scientific and engineering discipline that deals with the occurrence, distribution, movement and properties of water above and below the land surfaces of the earth. It deals with the relations and interactions of water with the environment, including biota. Hydrological studies allow for the planning, design and realization of water management measures for prospections, quantification, exploitation and efficient utilization of water resources in quality and quantity.

source: brittanica.com
source: brittanica.com

Key Terms:

Aquifer: an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, silt) from which water can be extracted using a water well.

Capillary rise: the ability of a liquid to flow in narrow spaces without the assistance of and in opposition to external forces like gravity.

Catena: a sequence of soils down a slope, created by the balances of processes, such as precipitation, infiltration and runoff.

Condensation: the change of water from its gaseous form (water vapor) into liquid water.  It generally occurs in the atmosphere when warm air rises, cools and loses its capacity to hold water vapor.  The excess water vapor condenses to form cloud droplets.

Depression storage (capacity): the ability of a particular area of land to retain water in pits and depressions, thus preventing it from flowing.

Effective precipitation: the amount of precipitation that is actually added to and stored in the soil (Amount of rain {mm} – 5) x .75).

Evaporation: the process by which water or other liquids change from liquids to a gas vapor; a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance.  The process requires heat from the sun.

Evapotranspiration (ET): the sum of evaporation and plant transpiration from the Earth’s land and ocean surface to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies.

Evection: the movement of water through the air.

Groundwater: the water present beneath the earth’s surface in soil pore spaces and in the fractures of rock formations.

Infiltration: one of the 6 processes that make up the water cycle; the rainwater soaks into the ground, through the soil and rock layers.

Interception: precipitation that does not reach the soil, but rather is intercepted by the leaves and branches of plants and the forest floor.

Interflow: water that travels laterally or horizontally through the zone(s) of aeration during or immediately following a precipitation event and discharges into another body of water.

Groundwater recharge (deep drainage/deep percolation): an area where water moves downward from surface water to groundwater.

Groundwater table: the surface of the groundwater exposed to an atmospheric pressure beneath the surface of the saturated zone.

Saturated zone: an area of an aquifer, below the water table, in which relatively all pores and fractures are saturated with water.

Sublimation: the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.

Surface runoff: precipitation that cannot be absorbed by the soil because the soil is already saturated that flows into another body of water; precipitation > infiltration.

Transpiration: the process by which moisture is carried through plants from roots to small pores on the underside of leaves where it changes to vapor and is released into the atmosphere.

 

the benefits of fire

forest fire
photo courtesy of NOAA

We have all read about them…the insane, previously unseen and completely out of control fires that are ravaging parts of America’s west. The lack of water has taken its toll. Reservoirs are tapped. Rivers are running dry. Famous people are illegally hoarding water. Lakes are at all-time lows. Northern parts of states are at odds with the southern parts. The state of Colorado wants its fair share of the Colorado River to stay in Colorado while Los Angeles keeps growing which means a higher demand for water. And then there are the scorching temperatures. The combination of drought conditions and high temperatures have resulted in widespread blazes which are often unpredictable and (unfortunately and unlikely) unavoidable – even with the best of land management plans (although there is always room for improvement).

This makes fires scary things to use human folks – as is the case with many things that we cannot control. This fear makes it easy to overlook the benefits of fire. However, the valuable role that they play in ecosystem health is undeniable.

Here are four benefits of fire in the health of our natural systems:

  • Fires clear underbrush which enriches the soil with new nutrients. This is known as nutrient cycling.
  • Fires help to eliminate invasive/non-native species.
  • Fires change the carrying capacity of forests by removing old growth, which is relatively unproductive, and opening up space for new and more varied growth.
  • Fires play a pivotal role in the perpetuation of various species. Hickory and oak trees, for example, have very thick bark which is able to sustain periodic fires. Furthermore, seedlings from these varieties their seedlings need nutrient-rich soil free of shade to thrive. In some locations, certain seeds require fire to germinate.  Fire also leaves behind acidic ash which is needed for the growth of native plants in places such as the sand plains.
photo courtesy of npr.org
photo courtesy of npr.org