SearchReSearch: Answer: What's the most significant thing going on here? (part 1/2)

I knew this would be a big Challenge...

... but it's a great example of the kind of SearchResearch questions that arise from the simplest of thoughts. Simple questions can quickly lead to deep / sophisticated research.

P/C Google Earth

The bigger question for us is this week is... how much has Lake Nasser changed the lands around it?

Here's a closeup of a piece of the Lake Nasser shore now:

As you can see, there are now a LOT of trees and bushes that are well-irrigated by the lake's rise and fall with the annual rains.

This is one effect of creating Lake Nasser, there are probably others. In particular, how does all of this new vegetation change the environment? Is it unimportant? Or does it profoundly change things?

For the last SRS Challenge of 2024, I'd like you to do a little bit of analysis and find out:

1. What has been the most important change in the Lake Nasser region since the lake was created in 1970? We know the effects of creating the reservoir for Egypt downstream of Aswan, but what about the region upstream (i.e., to the south)?

As I said, there's no single obviously correct answer to this question--and that's part of the point.

So... how does one approach such an all-encompassing question?

My first thought was to look for time-lapse images to get an overview. As we've discussed before (2017--Seeing Across Time; 2020--Time Lapse for Fires, there are handy time lapse Earth viewing tools (e.g., Google Time Lapse or the NASA Worldview site).

Let's dive into a time-lapse analysis and then take a second approach in the next post.

Here's a video that I made from the Google Time Lapse site showing the changes over the past 23 years:

This is one way to get a great overview of the area and the substantial changes that can be seen. Not only can you see the edges of the Nile fluctuate, growing and shrinking a bit with each season, but you can also see the sudden appearance in 1999 of a set of lakes that magically appear in 1999 (in the center of the images). These are the Toshka Lakes.

The Toshka Lakes appear when Lake Nasser has excess capacity and overflows its banks. As a precaution against any unexpected rise in Lake Nasser's water level, a spillway and channel were built in 1978. That spillway pointed towards the low-lying area that are now the Toshka Lakes.

In 1997, the Egyptian government decided to develop the Toshka Lakes region, where planned agricultural and industrial communities would develop. It has been an ambitious project which was meant to help Egypt cope with its rapidly growing population and create additional farmlands to feed the people.

Luckily for the government, the Toshka Lakes initially formed from massive flash floods and river floods in Ethiopia the next year (1998). The Aswan High Dam managed the flow for a while, but the flood control plan called for diverting excess water to the Toshka Lakes region. The excess water flowed through the spillway, just as planned and formed a series of lakes, just as planned. As a consequence, agricultural activity in the Toshka Lakes region rose rapidly in the 2000s, but soon the water levels of the lakes declined and became empty again by 2018.

You can see this in these side-by-side images taken from the video. The lakes appeared in late 1999 and show up first in the image from 2000. (They were large and obvious enough to be noticed by astronauts on the ISS.)

By late 2018, the lakes are empty (see center image below). The lakes are refilled after heavy rainfall in Sudan and South Sudan in the summer of 2019 with major flooding events in Sudan in 2020, 2021, and 2022.

Initially, the flooding of the low-lying depression was a side-effect of heavy rain pouring too much water into Lake Nasser. The depressions filled up with water, and voila--instant farmland. (It's unclear how much of this is a happy accident vs. pre-planned. It feels like there's a bit of revisionist history in the telling of the formation of Toshka Lakes from sites I can find.)

In any case, it's a real thing now, with a permanent canal--the Sheikh Zayad Canal--to keep pumping water from Lake Nasser from the Mubarak Pumping station into the Toshka Lakes, with lots of peripheral canals to water the farms. As you can see, they're mostly center pivot irrigation (previous SRS about center pivot), mostly growing wheat, tomatoes, onions, cucumbers, beans. okra, and green peppers.

Base map from Google Maps. Annotation by Dan showing the course of the Sheikh Zayad Canal.
The Mubarak Pumping Station is in the lower right on the shore of Lake Nasser.

While the canal was planned to be 320 km in length, currently only about 129 km (as I measured it on Google Maps)--that's a lot of canal, with plenty left to build.

All of this is pretty obvious by looking at the time-lapse images.

Building the High Dam at Aswan allowed for the entire Toshka Lakes project. It's a huge project that's been in process for 27 years, surviving as different governments come and go (and shift in their level of support--a characteristic for many multi-year goverment projects).

And it's also clear that there's a lot of shift in the lake shoreline as the rains vary from year to year. Here's a comparison of two different years at the Mubarak Pumping Station. Notice the differences between a high-water year and a low-water year.