Hydrosphere

The hydrosphere is related to water and the various systems it goes through. These include rivers, lakes, ocean, clouds and groundwater. Understanding how the hydrosphere works is of vital importance as life is dependent on it. Therefore it is important to look at how these different systems are linked together and how affecting parts of the cycle can affect society.

Water movement is linked by the hydrological cycle, a process in which water (referred to as a body during movement) is transferred between systems.

Simplistically the cycle begins with a reservoir e.g. lake or ocean, this holds a large enough body of water where output from evaporation is much less than input from streams or river.

The evaporated water molecules rise (as they are less dense) to the troposphere where they condense together due to the temperature decrease, causing them to lose energy.

This condensation of water molecules eventually forms clouds, a gaseous atmospheric reservoir which can be moved by air currents. Precipitation occurs when the accumulated water vapour gains enough mass that it can no longer be held in gaseous form and so forms liquid droplets that eventually fall as rain.

As clouds can essentially move it is common for rain to fall on land due to air currents, this continues the hydrological cycle (which is a land based cycle, if it were to precipitate into the reservoir then the cycle would be complete), as water infiltrates the ground, down into the bedrock where a water table forms or as surface water where it will flow as streams/rivers back to the ocean or lake.

Topographically the ground slopes out towards the sea, this means that the ground water in the bedrock flows downwards toward the sea, similar to surface water flow. The hydrological cycle finishes back at the ocean, as depicted in Fig 1.

Figure 3: simplistic model of the hydologic cycle (Retieved from; http://www.state.nj.us/drbc/library/images/hydrocycle2.jpg Date18/9/2015)

The hydrological cycle is the basis for the hydrosphere and for societies continued existence. It plays an important role in erosion of rocks and deposition of sediments and is an important factor in many geological processes. Therefore it is imperative that water management is put in place to manage the affects we have on the hydrological process and the water we take from it.

Water management and allocation are two important issues with regards to water use. Two examples of this are:

1.    California

2.    Canterbury NZ

California is in a current state of drought, as most of the state is covered in deserts, with the major cities located in dry, humid regions, meaning water doesn’t precipitate annually in many parts of California. Therefore most of its water has to be outsourced from other states, this has led to the Colorado river compact (CRC). The CRC was signed in the 1920’s as a means to equally divide the water resources of the Colorado River amongst Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming states.

Figure 4 States and Basin Areas of the CRC ( Retieved from: http://www.rand.org/content/dam/rand/www/external/jie/projects/RR242fig3-3.png Date 18/9/2015)

The compact splits the states into two groups:

1.    Upper Division; Colorado, Utah, New Mexico and Wyoming.

2.    Lower Division; California, Arizona and Nevada.

With each division being allocated 9251113914.9 cubic metres (7,500,000 acre-feet) of water per year (https://www.usbr.gov/lc/region/pao/pdfiles/crcompct.pdf date retrieved 18/9/2015).

This allocation is then further divided amongst the divisions in accordance to their individual regulatory compacts; Upper Colorado River Basin Compact 1946 and the Boulder Canyon Project signed 1928.

These two documents leave each state of the CRC with the following allocations Table 1

So what does this all mean?

The CRC is basically an agreement between seven states in America over water resource allocation. This however has led to an increase in issues and tensions between states in the last 20 years, as the CRC has many implications, which are:

·         It was a wet season when signed therefore more water available.

Early settlers to the Lower Division moved there during a wet season therefore a higher than average water flow, when the hydrological cycle records show that wet and drought seasons are an annual event.

·         One year’s observations were what it was based off.

The CRC is based off one year’s observations of water flow, thus making it highly inaccurate to base a model off let alone water resource allocation.

·         An over compensation.

The 9.25¹⁰ m³ of water is an unreasonable amount of water to be allocated, this has been shown with recent data collection showing that it is a lot higher than the mean average water flow (also see above points).

Canterbury New Zealand has developed a water contamination issue rather than shortage. The groundwater table for the Canterbury plains is progressively becoming contaminated with nitrate from fertiliser infiltration of farms. This has already generated a major issue in terms of drinking water as the city of Christchurch is dependent on this groundwater and now bore holes must be drilled past the first groundwater table due to contamination. 
As the cities water is predominantly sourced from the Waimakriri river to the north via groundwater systems, it allows for contamination to occur easily. 

What can be done?

For the California issue, a joint meeting between representative states should occur so that proper water allocation can be done ( as stated in article six of the CRC) using accurate data collected so that a better model and water allocation can happen.
In the case of Canterbury, better monitoring and control of nitrogen fertilisers is needed to control the issue, it would be foolish to assume that 100% removal of nitrate from the system can occur, as there will always be run off from farms.