DRAINMOD modelling for a Norwegian catchment

Fri, 01 Sep 2017 00:00:00 +0000

My MSc thesis at Wageningen University started from a simple question that turned out to be complicated: how does water actually move through an agricultural catchment in Norway?

I used DRAINMOD, a hydrological model originally built for poorly drained soils. It is used worldwide to design drainage systems, but mostly at field scale. I wanted to know whether you could push it to catchment scale, and whether it made sense in Norwegian conditions: mixed farmland and forest, hilly terrain, and soils that freeze and thaw.

The model let me run experiments on soil properties, drain spacing, surface storage, lateral conductivity and the temperature thresholds for freezing and thawing. Drain spacing and lateral hydraulic conductivity turned out to control the water balance. Surface storage mattered for peak flow. For sensitivity analysis the model worked well, because you could see which settings moved the system. It struggled with the hilly terrain and the spatial variation of a real catchment.

So DRAINMOD helped me understand how the system behaves, but it did not capture Norwegian drainage very well. It was built for flat fields, and this was a mixed, hilly catchment.

The full thesis is below.

Read the thesis

Mamanteo: old water harvesting in the Peruvian Andes

Fri, 01 Aug 2014 00:00:00 +0000

In 2014 I did my BSc internship and thesis in Huamantanga, Peru, on a centuries-old water system called mamanteo (amunas in Spanish). The name comes from Quechua and means something like “to nurture” or “to breastfeed”. The idea is that you nurse water out of the mountain.

In the rainy season, runoff from the mountainside is led into stone channels. These channels don’t bring the water to a village. They bring it to spots where the ground is permeable enough for the water to sink in. It then travels through the soil and, weeks or months later, comes out lower down in springs that people use in the dry season. You sow water in the mountain and harvest it later. The Wari culture may have used this since around 700 AD.

My fieldwork looked at where and why water infiltrates differently around these channels. I measured infiltration rates along the canals, looked at soil properties, and mapped the area to see how the builders had picked their infiltration zones. They were not placed at random. The channels targeted high-permeability zones and specific elevations, and places where vegetation helped the soil structure.

This matters for Lima, a city of over 10 million people in a desert, with only a few small rivers. Since 2016 mamanteo systems have been restored in several places in the Andes, and Peruvian agencies have found them cheap and hydrologically useful: no energy needed, natural filtering, little maintenance, and stone channels that last for centuries.

Earlier | Timon Weitkamp | No Worries, Just Maps

DRAINMOD modelling for a Norwegian catchment

Read the thesis

Mamanteo: old water harvesting in the Peruvian Andes