that may depend on the features in the catchment. If there is significant lateral outflow between two stations than it may be lower and vice a versa

Dear Jose

Basic questions are always difficult to answer. I will try to give you some information to understand upstream and downstream discharge.

Discharge is the flux of water during a unit time from a unit area. That is, the volume of water passes at a particular cross-section of a stream in a unit time; (Q=Av).

It is clear that water discharge depends on the cross-sectional area (A) and average flow velocity (v).

So the simplest answer to your question is that, if there is no change in area and no change in velocity then no change in discharge unless there is addition or lost of water :) Cheers!

Also,

1. Upstream has generally higher value than downstream due to water lost in different processes, but not always less as sometimes water could be added in downstream as well.

If there is a bridge and no water is lost then upstream of the bridge and downstream has almost equal discharge values.

Best Regards!

H!

I think the answer can be found in relate to morphometric parameters of catchment at the hydrometric station, and especially into the geology of catchment (e.g., limestone: infiltration!).

Best regards!

Dear Jose Valles,

During the flux of water through a streambed there should be losses due to infiltration (through the bed and banks of the stream), as well as influx of water by the shallow aquifer and lateral flow. Actually, you may consider certain the losses of water. If the distance between the upstream and downstream monitoring stations is long, it is quite possible that there will be influx of water by lateral flow, as well. It is quite unlikely that you get the same discharge values upstream and downstream, and even if you did it would be a coincidence. However, you cannot have any guarantees on whether the downstream discharge will be higher or lower than the upstream discharge. This would require a detailed study of the geomorphological features of your basin.

Good luck with your research!!

Hi Jose,

That would be determined on a catchment to catchment bases. Depending on where you are in the world, on the most basic level the discharges and volumes would increase as you move downstream. Think of a headwaters in a mountain starting off small, then as they move down the mountain they grow larger and larger.

However, keep in mind this depends on a number of parameters that would be unique to the catchment being studied. In contrast to increasing, it may be a losing stream (stream water is lost to GW) or be located in a high evaporation climate.

For the most part you will not be able to tell this on face value. I am guessing you are receiving the data, then determining why it is less or more. In that case ask yourself the questions that have been discussed above. Could it be a gaining or losing stream? What is the climate for the area? What is the geomorphology of the watershed? What is the vegetation cover? Could there be anthropocentric influences (agricultural/municipal)?

Best of luck!

Her for a certain river reach or stream catchment, reaches, the principle of water mass balance should be applied;

Qout = Qin+Runoff - + Subsurface lateral flow

Where: Qout is the measured discharge downstream of river reach.

Qin is the measured discharge upstream of river reach.

Hi Jose,

I would like to add just few notes.

One of the important things would be the distance between your discharge gauging stations and the ratio between catchment areas corresponding to these stations. The long distance between them can result in lower values of peak discharge in lower station due to flood wave transformation. This will depend on the parameters of the stream channel and the floodplain. On the other hand, the discharges can be also higher at lower station due to larger catchment area and of course more water. Generally, you can expect larger volume at downstream station due to larger catchment area. It is of course also important if we are speaking about flood discharges or discharges in rainless periods. The factors that are in my opinion important are:

• the geology and ground water regime (you can observe both inflow from groundwater as well as outflow to groundwater between the stations)
• morphology (lower longitudinal slope, the stream channel with low capacity, wide rough floodplain -> more possibilities for flood wave transformation
• technical structures on the stream such as bridges, culverts etc. which can play an important role in the transformation of the flood wave
• runoff conditions in the catchment and its shape which affect strongly runoff concentration

to conclude it, I would say that there is no general answer to your question. It would be necessary to know much more detail information about your case and it would also need relatively detail analysis of the conditions to give you more relevant answer.

Regards,

V.

Principle of mass balance i.e.

Qinflows = Qoutflows +_ change in storage

Calculate all the inflows and outflows including infiltration losses, piped in/ out water, surface runoff etc. The upstream flow will be a part of Qinflows n similarly downstream flow will be a part of Qoutflows.

Further to Trent Gay's answer above and for streams that are (on the catchment scale) loosing streams, I would add the following. For a stream to be “loosing”, there has to be inflow from upstream so typically these streams have a “gaining” upper section. The tipping point between loosing and gaining is then determined by climate (less rainfall downstream), geology (hard bedrock upstream, thick alluvial valley fillings downstream) etc. So, when you compare two gauges in an upstream gaining reach, the downstream gauge would typically have more flow than the upstream gauge, while in the loosing reaches the opposite would be the case – the further downstream you go, the less flow you will observe. And somewhere along the river, there is a point where the maximum flow occurs, and this point is expected to shift from year to year depending on amount of rainfall and resulting runoff.

All the above from the perspective of total flows, not peak flows.

Dear friend: Also, you should verify if the gauge station are altered or natural stations. Also, you should analyse the potential demand and/or inflows into the reach between 2 stations. If you have a natural basin, it is supposed that, at higher basin, higher flow.

Jose Valles i would like to mention is In order for water to flow, the cross-sectional area (A) and flow velocity (v) must be taken into account. Due to the amount of water that is lost in various processes, upstream is generally more valuable than downstream. However, this is not always the case, as water can be added in the downstream as well.