Different resolutions

Taking up where we left off in the previous post, we are going to explore the spatial and temporal resolution. I am going to summarize key points from Watts, 2010 .

2.   Spatial resolution 

Models can cover different spatial scales from few centimeters to hundreds of kilometers. Hence, depending on the hydrological problem of interest, the spatial resolution can be chosen according to the details that are to be described.  For instance, global hydrological cycles are of hundreds of kilometers in spatial resolution. Such models require to be broken down into smaller geographical units. This is where distributed models come into the picture. Spatially distributed models process the geographical units and produce results for each of them. So the whole catchment is divided into sub areas. 

On the opposite side there are lumped models, where the whole hydrological system is considered as a single unit. For example a lumped model of a catchment might consider only one point flow into the system and give an averaged values for parameters such as soil moisture content. 

Semi-distributed models sit between the lumped and distributed models. These models are usually a series of lumped models.

           3.       Temporal resolution 

Hydrological models can be considered with different time-steps that could range from few seconds to years. Some other models give averaged values over a long time period. Model formulation has an impact on the chosen time resolution. For instance, complex numerical models may behave unstable when considering long time-steps.  So it is up to the modellers to choose the appropriate time resolution for the problem being addressed. 

So as we saw from this post and the previous post, there are different factors and scales that modellers should consider when making the decision of choosing a modelling approach. Next we are going to see what the tools of decision making are when choosing a modelling approach.

Till next time,

Variety is the spice of modelling!

There are many different modelling approaches that can be used in hydrology, which is quite interesting and useful as it brings more options for modellers to choose from according to their need. So it’s pretty cool in that sense but it is very important to not get so carried away so that the main purpose is lost or the quality and usability are downgraded. And it often more logical to seek the simplest model that can efficiently address the problem of interest.

It is quite useful to consider three different modelling dimensions (Watts, 1997 cited in Watts, 2010)

1. Theoretical complexity
2. Spatial resolution
3. Temporal resolution

Today we are going to investigate different models with different theoretical complexity levels.

Three models can be considered while considering the theoretical complexity level. From simple models to more complex are Empirical models, Conceptual models, and physically based models. 

Empirical models are the simplest and describe how the system behaves without getting into details of the physical processes. These simple models usually use statistical data. 

Conceptual models are a bit more complex. These models represent a simplified behavior of catchments on perceived behavior of the catchment rather than getting into details of the physical characteristics of the catchment. For example a conceptual catchment model thinks of the soil medium as a bucket that accommodates recharge for groundwater when it reaches its full capacity.

Next level of complexity is for physically based models. These models try to represent the physical process of water movement in the catchment. This method uses the physically based equations and often are parameterized by the catchment characteristics such as soil properties that are measurable in the laboratories (Watts, 2010).

Join me on the next post where we explore the spatial and temporal resolutions. After having gained some information on the available approaches we shall see which one is more appropriate when looking at water availability under the impacts of climate change. 

So long

The rights and wrongs of IWRM

Water management is a foundation upon which safe drinking water, agriculture, food production, protection from floods and droughts, energy production, and the sustenance of ecosystem relies. 

There are different aspects into water management, three of which I've put in the diagram below.And as discussed in "what's the big deal?" post, they are influenced by both climatic and non-climatic factors. Good news is that modelling is used in all three of them ! GO MODELLING! well I meant Environmental Modelling...

The Integrated Water Resource Management (IWRM) has been defined by GWP (Global Water Partnership) as "a process which promotes the coordinated development and management of water, land and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems."

Well, to be honest that definition to me is quite vague. So I tried to look into it more from the same source and according to GWP, the concept challenges the traditional, fragmented water management and water developments to put emphasis on integrated approach with more coordinated decision making between different sectors(GWP,2013).

source:GWP

Ok, that’s a bit better. It turns out that I’m not the only one feeling confused about the definition. According to an interesting article by Mitchell,Bellete and Richardson (2014) , the concept is not properly defined and the definition from GWP is not used consistently. Hence, there are multiple definitions of IWR which cause ambiguity. The paper talks about how distinction should be made between  “holistic” or “comprehensive” and "integrated" approaches. The first two are all-inclusive by definition. So, the objective is to include and consider all the variables and the links between them.

Such method of approach helps to make sure that no significant variable or relationship is overlooked. However, a disadvantage of an all-inclusive approach may be the fact that it can become overwhelming in the sense that examining all of the interconnections may not be possible. However, an integrated approach supports the importance of understanding the interconnections between different variables, but puts focus only on those that are key players for change and susceptible to being managed. 

So some points to keep in mind about IWRM and IWM:

•   For IWRM to be a useful approach, it is crucial to have a better, more precise definition as the word “integration” does not have a common definition(Mitchell,Bellete and Richardson ,2014). Furthermore, it is important that the definition is consistently used throughout practices.

•   IWM can successfully be achieved with high level of participation and cooperation between providers of water, protectors of water , and users of water (CIWEM,2011).

• One of the main advantages and main motivations for Integrated management approach is to overcome and prevent the “silo effect”- when different agencies and sectors only focus on their own interests and responsibilities! 

Silo effect-source:

Having said all of this, it should be acknowledged that water management is never “solved” and that it is an ongoing process (CIWEM,2011). 

We shall look into the role of modelling in management in future posts

Adios,

Don't take it for granted!

So this week I was looking for some documentaries to watch and “Last Call at the Oasis” caught my attention. This is an eye-opening documentary about water which was produced in 2012.

I found it as a very good documentary that looked into some of the different aspects of water management such as water availability, water pollution, public perception, politics, different sector demands, and economy.

It shows the evidence of Climate Change on water cycle and how as we discussed in the last post, it is causing more droughts and more floods. One of the scariest part of the documentary for me was how early conflicts are getting started over water within a country. I had my fright night right then. When they proposed to pipe water from an oasis with population of merely 150 to Las Vegas with population of over 2 million , you hear people saying"This project may succeed over my dead body".

To see that fight over water is happening within one country, makes the idea of wars between different nations not so far-fetched! As Ismail Seragedin said: "The wars of the 21^st century will be fought over water".

The documentary also shows how the trend of water pollution is continuing from Cuyahoga River fire in 1969 that made firemen to pour water on water (!) to current carcinogenic substances.

Cuyahoga River fire-source:time.com

The example of Hoover damn, which is on the border between the U.S. states of Arizona and Nevada, and is facing the risk of not being in operation due to lack of water elevation, showed how economy is intertwined to water scarcity.

Hoover Damn with loss of water elevation-source:hcn.org

Even though I managed to make my family watch this with me-and they really liked it too- I cannot make you guys to watch it but I definitely do recommend it.

This question has been occupying my mind: Can we reverse the situation? Or is it that issues such as Climate Change are not reversible and it just comes down to managing the situation? and the question got even more challenging after the Geoenginnering seminar, just looking at what kind of ideas are being researched to reverse the Global warming and try to cool down the planet. 

Anyway, I shall leave you with that question,

As Erin Brockovich’s dad sang to her: “See that lovely water trickling down the spring, don’t take it for granted someday it might not be seen”, let’s not take it for granted...