Subject: unmet water catchment Posted: 1/15/2025 Viewed: 663 times
In my study area, I have an agricultural land utilizing a catchment system. This land is cultivated with multiple crops. Based on the results from a weap21-based program, there is evidence of water deficit in the agricultural fields. Despite this water deficit, some crops were negatively affected due to the lack of water, while others remained unaffected. Interestingly, for the unaffected crops, the actual evapotranspiration and potential evapotranspiration were equal, and their productivity did not decline when compared to the affected crops, whose productivity was significantly reduced. It is important to note that the crops were planted almost at the same time.
What could be the reason why some crops were negatively impacted while others were not?
I would appreciate your assistance. Thank you
Mr. Doug Chalmers
Subject: Re: unmet water catchment Posted: 1/15/2025 Viewed: 654 times
Kinan,
Are you referring to the change in crop yield with a change in water supply? This will be defined by the Yield Response Factor. This defines the decline in crop yield that occurs as the ET Actual falls below the ET Potential. You mention that your ET Actual is the same as the ET Potential for the crops whose yields were not affected. This would be the expected result. Is it possible that the unaffected crops have lower ET demand than the expected crops?
Hope this helps!
-Doug
Eng. kinan alahmad
Subject: Re: unmet water catchment Posted: 1/15/2025 Viewed: 643 times
Thank you for your response, Mr. Doug.
Based on the observed results, two cases were identified for the crops:
Case 1: Certain crops, such as legumes and potatoes, were not affected by water deficit. In these cases, the potential and actual evapotranspiration were identical, resulting in stable production per ton. Therefore, the yield did not decrease due to the water deficit.
Case 2: Other crops, such as wheat and barley, were adversely affected by the water deficit. In this case, the actual evapotranspiration was lower than the potential evapotranspiration due to water scarcity, leading to a decrease in productivity.
The question arises: why were some crops affected by water deficit while others remained unaffected, considering that the crops were planted roughly during the same period?
Mr. Doug Chalmers
Subject: Re: unmet water catchment Posted: 1/15/2025 Viewed: 636 times
Are the potential ET demands of these crops different? It sounds likely that Case 1 would have lower potential ET demand than Case 2. Case 1 may be able to be fulfilled by rainfall alone, or with lower water supply.
-Doug
Eng. kinan alahmad
Subject: Re: unmet water catchment Posted: 1/16/2025 Viewed: 627 times
Thank you for your attention, Mr. Doug.
Yes, there is a significant difference in the water requirements for different crops. For example:
One hectare of wheat requires 2,300 cubic meters of water.
Barley requires 1,200 cubic meters.
Legumes require 2,000 cubic meters.
Potatoes require 4,500 cubic meters.
Sugar beets require 6,000 cubic meters.
I would like to inform you that the agricultural land is divided into five crops, with wheat and barley occupying 80% of the total land area. These crops have been severely affected by the water shortage.
However, crops like potatoes, sugar beets, and fava beans, which account for 20% of the land, have not been affected by the lack of water.
Does the system prioritize supplying water to the crops with smaller areas first, and then to those with larger areas, even though all of them are in the same catchment node? Or is there another reason for this approach?
Mr. Doug Chalmers
Subject: Re: unmet water catchment Posted: 1/16/2025 Viewed: 619 times
Kinan,
Are all of these crops branches in a single catchment? Or each crop is a different catchment? What hydrology method are you using?
Eng. kinan alahmad
Subject: Re: unmet water catchment Posted: 1/17/2025 Viewed: 587 times
Mr. Doug,
All the previously mentioned crops have been added as branches to the same catchment node.
The method used is MABIA
Mr. Doug Chalmers
Subject: Re: unmet water catchment Posted: 1/23/2025 Viewed: 418 times
Kinan,
My understanding is that water is allocated to each branch in equal percentages of their demand. So, each branch/crop can have different soil moisture values. Without knowing too much about the crops, my guess would be that either the crops have different growing periods or their yield factors are different, such that the crop yields react to shortages differently. These factors are included in the crop library and can be edited.
-Doug
Eng. kinan alahmad
Subject: Re: unmet water catchment Posted: 1/26/2025 Viewed: 241 times
Thank you for your interest.
